Stoichiometry - clear & simple (with practice problems) - Chemistry Playlist

Summary

The video script offers an engaging and comprehensive guide to understanding stoichiometry, emphasizing its simplicity by breaking it down into four basic problem patterns. It compares stoichiometry to baking, highlighting the importance of balancing chemical equations and calculating mole ratios. The script also differentiates between ideal and limiting reactant stoichiometry, providing clear examples and methodologies for solving problems with moles and mass conversions. It encourages viewers to practice these concepts to master stoichiometry, promising ease in solving complex chemistry problems.

Takeaways

• 📚 Stoichiometry is a fundamental concept in chemistry that involves the quantitative relationships between reactants and products in chemical reactions.
• 🔍 The speaker emphasizes that understanding only four types of stoichiometry problems can significantly simplify the learning process: mole to mole, mole to mass, mass to mole, and mass to mass.
• 🧐 The transcript uses the analogy of baking to explain stoichiometry, highlighting that it's about measuring ingredients to achieve a desired product, similar to balancing chemical equations.
• 🔢 Balancing chemical equations is a crucial first step in stoichiometry, which involves ensuring that the number of atoms for each element is the same on both sides of the equation.
• 📉 The video script discusses the difference between ideal stoichiometry, where reactions are assumed to have perfect conditions, and limiting reactant stoichiometry, which is more realistic and accounts for reactions where one reactant is depleted first.
• 📝 The speaker introduces five key skills needed to master stoichiometry: balancing chemical equations, determining stoichiometric coefficients, understanding mole ratios, distinguishing between ideal and limiting reactant stoichiometry, and solving a variety of stoichiometry problems.
• 🔄 The concept of mole ratios is explained, which involves the relationships between different substances in a balanced chemical equation, allowing for the calculation of reactant and product amounts.
• 📉 The script uses the example of aerobic metabolism of butyric acid to illustrate how to balance a chemical equation and calculate stoichiometric coefficients.
• 📚 The importance of understanding significant figures in stoichiometry calculations is highlighted, ensuring that the answer reflects the precision of the given data.
• 📈 The transcript outlines a step-by-step methodology for solving stoichiometry problems using dimensional analysis, which involves setting up conversion factors and canceling units to find the desired quantity.
• 🔑 The speaker provides practice questions related to stoichiometry, encouraging viewers to apply the concepts learned in the script to solve them, thus reinforcing the learning process.

Q & A

What is the meaning of the term 'Stoichiometry'?

Stoichiometry refers to the quantitative relationships between reactants and products in a chemical reaction. The term comes from 'stoichio' meaning element and 'metri' meaning measurement.

Why is it important to balance chemical equations before performing stoichiometric calculations?

Balancing chemical equations is crucial because it ensures that the number of atoms for each element is the same on both sides of the equation, allowing for accurate stoichiometric calculations.

What are the four basic patterns of stoichiometry problems mentioned in the script?

The four basic patterns of stoichiometry problems are mole to mole, mole to mass, mass to mole, and mass to mass.

What is the difference between ideal stoichiometry and limiting reactant stoichiometry?

Ideal stoichiometry assumes that there is an unlimited supply of reactants and no loss, resulting in 100% yield. Limiting reactant stoichiometry, on the other hand, takes into account that one of the reactants may run out before the reaction is complete, limiting the amount of product formed.

How many significant figures should be used when reporting the number of moles of calcium in the average human body, according to the script?

The script suggests using four significant figures when reporting the number of moles of calcium in the average human body.

What is the concept of 'mole ratios' in stoichiometry?

Mole ratios in stoichiometry refer to the relationships between the amounts of reactants and products in a balanced chemical equation, allowing for the conversion between different quantities of substances involved in a reaction.

What is the correct name for the substance 'CoCl2.6H2O' as discussed in the script?

The correct name for 'CoCl2.6H2O' is Cobalt(II) chloride hexahydrate, indicating a compound with Cobalt in the +2 oxidation state and six water molecules of hydration.

What is the philosophy of Stoicism, and how does it relate to the concept of stoichiometry?

The philosophy of Stoicism is an ancient school of philosophy that promotes the idea of accepting whatever happens in life. In the script, it is used as a metaphor to emphasize the importance of keeping things simple and basic in stoichiometry, similar to the stoic approach to life.

How does the script compare stoichiometry to baking a cake?

The script compares stoichiometry to baking a cake by explaining that just as you need specific amounts of ingredients to bake a cake, you need specific ratios of reactants to produce a certain amount of products in a chemical reaction.

What is the purpose of the 'five steps to surviving chemistry' methodology mentioned in the script?

The 'five steps to surviving chemistry' methodology is a systematic approach to solving stoichiometry problems. It involves starting with the given information, using dimensional analysis to set up conversion factors, repeating the process as needed for multiple conversions, performing the math, and reporting the answer with the correct units.

Outlines

00:00

😀 Overcoming Stoichiometry Fears

The paragraph introduces the concept of stoichiometry, emphasizing that it's not as daunting as one might think. The speaker uses humor to encourage the audience, stating that if they can understand it, anyone can. The focus is on recognizing four main types of stoichiometry problems: mole to mole, mole to mass, mass to mole, and mass to mass, which are essential for mastering the subject. The analogy of baking is used to simplify the concept, likening chemical reactions to following a recipe. The paragraph concludes with an introduction to the video series and a teaser about the simplicity of ideal stoichiometry problems.

05:02

🔍 Balancing Chemical Equations and Stoichiometric Coefficients

This paragraph delves into the first skill required for stoichiometry: balancing chemical equations. The speaker guides the audience through the process of balancing an equation step by step, emphasizing the importance of having equal atoms on both sides of the equation. The concept of stoichiometric coefficients is introduced, explaining that these are the numbers in front of the chemical formulas that indicate the amounts of reactants and products. The paragraph also touches on geometric coefficients and mole ratios, setting the stage for understanding more complex stoichiometry problems.

10:03

🧪 Understanding Ideal vs. Limiting Stoichiometry

The speaker contrasts ideal stoichiometry, where reactions proceed with an abundance of reactants and 100% yield, with limiting reactants stoichiometry, which reflects more realistic conditions where one reactant is depleted before the reaction is complete. The paragraph uses the analogy of baking a cake with limited ingredients to illustrate the concept of limiting reactants. The speaker also introduces the method of dimensional analysis for solving stoichiometry problems, providing a step-by-step approach to convert between different units of measurement.

15:04

📚 Applying Stoichiometry to Butyric Acid Metabolism

The paragraph presents a practical example of stoichiometry by examining the aerobic metabolism of butyric acid, which is assumed to yield carbon dioxide and water as products. The speaker challenges the audience to balance the chemical equation for this reaction and determine the stoichiometric coefficients. The focus is on applying the concepts learned in previous paragraphs to a biochemistry context, further emphasizing the importance of balancing equations and understanding mole ratios.

20:05

🔢 Solving Stoichiometry Problems with Dimensional Analysis

This paragraph demonstrates how to use dimensional analysis to solve stoichiometry problems involving different units of measurement. The speaker provides a step-by-step guide on converting moles of reactants to moles of products, and then to grams, using the balanced chemical equation as a conversion factor. The emphasis is on the process of cancellation and the importance of significant figures in scientific calculations.

25:06

🧐 Advanced Stoichiometry Problem Solving

The speaker increases the complexity of the stoichiometry problems, guiding the audience through mass-to-mole and mole-to-mass conversions. The paragraph illustrates how to approach problems that require multiple steps, such as converting grams of one substance to grams of another in a chemical reaction. The speaker reiterates the importance of balancing equations and using dimensional analysis to solve for the desired quantities.

📘 Summarizing Stoichiometry Concepts and Inviting Engagement

In the final paragraph, the speaker summarizes the key concepts covered in the script, including balancing chemical equations, understanding stoichiometric coefficients, and applying dimensional analysis to solve stoichiometry problems. The speaker invites the audience to engage with the content by answering questions related to the human body's calcium content and a stoichiometry problem involving aluminum and oxygen. The paragraph concludes with an invitation to support the channel and a reminder of the educational resources available.

Keywords

💡Stoichiometry

Stoichiometry is the quantitative aspect of chemistry that deals with the relationships between the amounts of reactants and products in chemical reactions. It is central to the video's theme, as the script emphasizes that understanding stoichiometry is crucial for mastering chemistry. The video explains that stoichiometry involves balancing chemical equations and calculating mole ratios, which are essential for determining the quantities involved in reactions.

💡Chemical Equation

A chemical equation is a representation of a chemical reaction, showing the reactants and products along with their stoichiometric coefficients. In the video, the script stresses the importance of balancing chemical equations as the first step in solving stoichiometry problems, ensuring that the number of atoms of each element is the same on both sides of the equation.

💡Mole Ratios

Mole ratios are the relationships between the amounts of substances in a chemical reaction, typically expressed in moles. The video explains how to determine mole ratios from a balanced chemical equation, which is essential for performing stoichiometric calculations and understanding how much product can be formed from a given amount of reactants.

💡Ideal Stoichiometry

Ideal stoichiometry refers to the theoretical calculations based on the assumption that reactions proceed with perfect efficiency and that there are no limiting reactants. The video contrasts this with limiting reactants stoichiometry, where not all reactants are fully converted into products due to one being in shorter supply. The script uses the concept of baking a cake to illustrate ideal stoichiometry, where having the exact amounts of ingredients results in the desired product.

💡Limiting Reactants

Limiting reactants are the substances in a chemical reaction that are completely consumed and thus determine the maximum amount of product that can be formed. The video introduces the concept of limiting reactants stoichiometry, where the script explains that in real-life scenarios, reactions often do not proceed with ideal conditions, and one reactant may run out before the reaction is complete.

💡Dimensional Analysis

Dimensional analysis is a systematic approach to converting between different units of measurement, often used in stoichiometry to relate the amounts of reactants and products. The video script describes using dimensional analysis to set up conversion factors that allow for the calculation of unknown quantities in stoichiometry problems.

💡Stoichiometric Coefficients

Stoichiometric coefficients are the numbers that appear in front of the chemical formulas in a balanced chemical equation, indicating the relative amounts of reactants and products. The video emphasizes the importance of identifying these coefficients after balancing an equation to perform stoichiometric calculations.

💡Hydrate

A hydrate is a compound that includes water molecules as part of its chemical structure. In the script, the term is used to describe a specific type of compound, such as cobalt chloride hexahydrate, where 'hexa' indicates the presence of six water molecules in the compound's formula.

💡Aerobic Metabolism

Aerobic metabolism refers to the process by which organisms use oxygen to break down substances like glucose to produce energy, carbon dioxide, and water. The video script uses the term in the context of writing a balanced chemical equation for the aerobic metabolism of butyric acid, emphasizing the importance of understanding biochemical processes in stoichiometry.

💡Significant Figures

Significant figures are the digits in a number that carry meaningful information about its precision. The video script mentions the importance of retaining the correct number of significant figures in stoichiometry calculations to ensure the accuracy and reliability of the results.

💡Mole to Mass Conversion

Mole to mass conversion is the process of converting the amount of a substance from moles to mass, which requires knowledge of the substance's molar mass. The video script describes how to perform mole to mass conversions in the context of stoichiometry problems, illustrating the multi-step process with examples.

💡Mass to Mole Conversion

Mass to mole conversion is the inverse of mole to mass conversion, where the mass of a substance is converted into moles using its molar mass. The video script explains the steps for mass to mole conversions, emphasizing the importance of this skill in solving stoichiometry problems involving different units.

Highlights

The transcript emphasizes that having a fixed mindset about the difficulty of stoichiometry can hinder understanding, suggesting that even those who consider themselves less capable can grasp the concept.

Stoichiometry is simplified into four main problem types, which, once understood, can greatly ease the process of solving related chemistry problems.

The concept of 'stoichiometry' is linked to everyday activities such as baking, where measurements of ingredients are crucial, just as measurements of elements are in chemical reactions.

The importance of correctly naming chemical substances is highlighted, with an example provided to illustrate the correct naming of 'CoCl2.6H2O'.

The transcript introduces the philosophy of stoicism and relates it to the basic elemental approach in chemistry, suggesting a connection between philosophical and scientific simplicity.

The process of balancing chemical equations is detailed, emphasizing its necessity for accurate stoichiometric calculations.

Understanding mole ratios is presented as a key component of stoichiometry, allowing for the relationship between different substances in a reaction to be quantified.

The difference between ideal and limiting stoichiometry is explained, with the former assuming unlimited reactants and the latter reflecting real-world scenarios where reactants may be limited.

The transcript provides a step-by-step guide on how to approach stoichiometry problems, advocating for a methodical approach using given information and dimensional analysis.

An example of calculating moles of carbon dioxide from moles of oxygen is given, demonstrating the application of stoichiometric ratios in problem-solving.

The concept of significant figures in chemistry calculations is introduced, showing the importance of precision in reporting results.

The transcript explains how to convert between moles and grams in stoichiometry, a crucial skill for solving problems involving mass.

A method for solving mass-to-mass stoichiometry problems is outlined, involving multiple steps of conversion and calculation.

The transcript uses the example of aerobic metabolism of butyric acid to illustrate the application of stoichiometry in biochemistry.

The importance of balancing chemical equations before performing stoichiometric calculations is reiterated, with examples provided to demonstrate the process.

The transcript concludes with a series of questions for the viewer to practice their newly learned skills, reinforcing the concepts taught.

Transcripts

if you have already decided that you

will never understand Stoichiometry

equations then you are already toast

there is no hope for you because you

already made up your mind but trust me

it is not that hard if a doofus like me

can understand it then you can too ideal

Stoichiometry only has four shapes or

patterns of problems multiple mess to

mole or Mass to mass if you can only

grasp these four types of Stoichiometry

problems you will be in a very good

shape if it ends in metri it means what

measurement and think of Stoichiometry

like baking please watch the videos in

this chemistry quick review playlist in

order let's start by answering the

question of last video what's the

correct name of this substance

cocl2.6820 please pause and try to

answer this yourself remember uppercase

C uppercase o is carbon monoxide however

uppercase C lowercase o is Cobalt Cobalt

followed by chlorine is Cobalt

chloride not chlorine because that's a

compound but do we have more than one

type of cobalt of course we have Cobalt

Roman numeral two and Cobalt Roman

numeral three Cobalt 2 is divalent but

couple III is trivalent and since

chlorine is monovalent the one is here

and not written Cobalt here is divalent

because I see two here so this is Cobalt

Roman numeral two chloride am I done yet

no I have six Waters after a DOT so it's

a hydrate how many water molecules six

so this is

hexahydrate so the final answer is

Cobalt Roman numeral two chloride

hexahydrate hydrates and anhydrous

crystals were discussed in the last

video with their problems and solutions

today it's time to talk about

Stoichiometry stoichio means element

which is the most basic form of matter

and metri means measurement have you

ever heard of the philosophy of stoicism

which is the exact opposite of

epicureanism if so what does it remind

you of oh something basic Elemental keep

it simple who knows if anything is good

or bad

epicureanism however is the exact

opposite let us eat and drink because

tomorrow we shall die only medicosis can

make General chemistry so profound as

the famous late historian will Durant

once said quote a nation is born stoic

and dies a picurion unquote

Stoichiometry is just like baking if in

order to make one cake I need one pound

of flour one pound of sugar and four

eggs I will make one cake but what if I

have only half a pound of flour half a

pound of sugar and two eggs can I make

an entire cake no can I make half a cake

yes this is all about psychiometry

measuring the element measuring the

ingredients to get a certain product but

what if I have double the amount of

flour double the sugar double the eggs

you can make two cakes

Stoichiometry is the exact same concept

nothing more nothing less so if you want

to master the subject of Stoichiometry

you need to acquire just five skills

that's it first how to balance the

chemical equation and we talked about

this before in this chemistry quick

review playlist how to figure out this

stoichiometric coefficients and you can

only do this after balancing the

chemical equation next to figure out

mole ratios after this is to understand

the difference between ideals to

econometry and limiting reactant

stoichiometry in today's video we'll

talk about ideal Stoichiometry and in

the following video we'll talk about

limiting reactants to echiometry after

that the subsequent video will be about

solving as many Stoichiometry problems

as humanly possible if you just watch

these three videos I promise you you

will cruise through Stoichiometry like a

sharp knife through warm butter in ideal

Stoichiometry today's topic will learn

four patterns of problems multiple

conversions just one step the easiest

type of Stoichiometry problems if you

get one of these on your exam you should

leave the exam room go outside dance for

a while and then come back to solve the

problem that's how good they are they

are so simple mold to mass and mass to

mold take two steps to answer mess to

mass that's the boogeyman you need to

leave the exam room go outside start to

weep cry cuss sprinkle some dust

particles on your forehead as they did

in the good old days and then come back

to try to answer these questions just

four patterns of problems even a child

can recognize four different patterns oh

that's a puppy that's a horse that's an

elephant that's a giraffe but first

things first if your equation is not

balanced there is no hope for you get

guaranteed to answer the question

incorrectly so the first skill is to

balance the chemical equation please

pause and try to balance this thing

let's do it start with the Silicon okay

how many silicones do we have here just

one and on the other side also one so

we're good let's look at the next one

chlorine I have four chlorine atoms here

and just one chlorine atom here okey

dokey let's multiply this by 4 and see

how many chlorine here I have four atoms

and four atoms so we're good let's look

at hydrogen here I have two hydrogen

atoms but here I have two plus four is

six oh so how can I make it balance

let's multiply this by three so here I

have six hydrogen atoms and two plus

four is six hydrogen atoms so hydrogen

is good let's look at oxygen I have

three oxygen atoms here and three oxygen

atoms here voila my chemical equation is

balanced balancing the chemical equation

will enable me to get the coefficients

right so after balancing this equation

can you tell me what are the

stoichiometric coefficients in this

lovely balanced chemical equation please

pause and try to answer this yourself

okay so it's very easy basically the

coefficients are these numbers okie doke

so here I have one which is not written

three and then I have one I have four so

the stoichiometric coefficients in the

equation are one three one and four how

about this question which we have

reviewed before what are these two

geometric coefficients in the

aforementioned equation when it's

balanced so let's go pause and try to

answer this yourself let's balance the

equation how many Silvers here just one

how about here two so if I try to

multiply this side by two I'll have two

iodits but I have three iodines here oh

two versus three what do you do well

whenever in doubt you place a 6 here why

six iodines amazing and and to make this

6 you multiply this by 2. let's see if

the iron is balanced I have two iron

atoms here and two iron atoms here

amazing iodine six iodines and six

iodines Silver Six Silvers and two

Silvers how about multiplying this by

three now I have six solvers and six

solvers Mr carbon I have three carbons

here and on the other side I have three

carbons there perfect oxygen three times

three is nine oxygen atoms and three

times three is nine oxygen atoms this is

my balanced chemical equation now what

are these stoichiometric coefficients

six one two and three so the correct

answer here is e as an equation after

mastering the first two skills let's

talk about skill number three mole

ratios take a look at this wonderful

equation that we have just balanced we

have reactants on the side and product

on the other side and the arrow means

yields the reactants react together to

yield the products let's suppose that

this is a this is B we'll call this C

and this one is d i can get any ratio I

want I can get a to B which means 6

moles of AGI to one mole of fe2 CO3 all

three how about a to c sure put the six

moles of AGI on the numerator and the

two moles of fei3 and the denominator

how about a to d we can do this as well

6 moles to three moles how about B to C

similarly we can do this you can do any

race you want so we have six possible

ratios and these ratios will be

exploited by your professor in your exam

next is to understand the difference

between ideal Stoichiometry and limiting

reactants to a geometry ideal means

ideal conditions in la la land that does

not really exist it assumes that we have

every anything in the perfect most

abundant proportions we will not run out

of any ingredients I.E reactants no loss

of reactants and 100 percent yield for

products everything is hunky-dory

however in reality most reactions are

limiting reactants Stoichiometry

assuming more realistic conditions not

this La La Land only some reactant

molecules go through the chemical

reaction and yield not 100 of the

product but we'll assume most of the

products we did not start with enough

ingredients we ran out of one of those

reactants first which limits the amount

of the products formed example I expect

to make one cake so I want one pound of

flour one pound of sugar okay I have

those let's look in my refrigerator I

did not have four eggs I only had two

eggs oh that's a limiting reactant with

this in mind do you think I'll be able

to make an entire cake no you will not

make 100 end of the cake because your

reaction was limited by one reactant now

let's get real butyric acid also known

as betanoic acid

c4h8o2 is aerobically metabolized we'll

assume that carbon dioxide and water are

the only products please write down the

balanced chemical equation and the

stoichiometric coefficients of each

agent please pause and try to solve this

yourself remember from biochemistry what

does aerobic metabolism mean if you've

watched my biochemistry playlist or my

biology playlist you know that aerobic

metabolism meaning metabolize something

in the presence of oxygen to yield what

carbon dioxide and water this metabolism

happens every day in your body but we do

not start with butyric acid instead with

salt with glucose most of the time and

your cells will release carbon dioxide

which you exhale and water in many forms

such as water vapor you will exhale this

as well and and just good old water

which you will urinate and or sweat Etc

so this is my equation before balancing

let's balance the equation okie dokie it

becomes like this four carbons on this

side four carbons on the side eight

hydrogens on the side four times two is

eight hydrogens on the side two oxons

here and ten axons here is twelve and I

have four times two is eight oxygens and

four oxygens also 12. so I just balance

the equation what are these two

geometric coefficients of each agent I

have one I have five I have four and

four using the same equation that you

just balanced in an ideal reaction I.E

ideal Stoichiometry assuming everything

is hunky dory and we're not running out

of anything a 4.25 moles of oxygen react

how many moles of carbon dioxide could

be formed please pause and try to answer

this yourself the reason you're

struggling with Stoichiometry is because

because we haven't organized your

thoughts there are only four

possibilities they can ask you mall to

mall or mall to mass or mass to mole or

Mass to mass multiple is just one step

mol to mass and mass to mole two steps

each Mass to mass is the horrible one

three steps regardless of the

methodology regardless of the pattern we

can follow these steps thank you again

the great teacher Julie C jilbert and

her wonderful book five steps to

surviving chemistry step number one

start with the given info and then

dimensional analysis time you set up a

conversion factor ratio whatever you're

starting from goes in the denominator

whatever you're aiming at whatever

you're converting to goes in the

numerator and then you cancel top bottom

Etc repeat step number two as many times

as needed sometimes we repeat it once

more to mole conversions sometimes we

repeat it twice more to mass or mass to

mole and sometimes we do the same thing

think three times mass to mass problems

do the math cancel top and bottom and

then give me your numerical value and

don't forget the measuring unit we will

use these steps to answer and solve this

problem let's go 4.5 moles of oxygen

react then how many moles of carbon

dioxide could be formed now do you think

this is mole to mole mole to mass mass

to mole or Mass to mass kind of problem

let's see moles of oxygen and moles of

carbon dioxide this means mole to mole

conversion and if it's mole to mole

problem we only need one step woohoo

this is easy so let's follow the

methodology step number one you start

with the given okay what's the given

4.25 moles of oxygen okie dokie and then

what you start to aim at carbon dioxide

so let me set up a dimensional analysis

conversion factor ratio let me put mold

of oxygen downstairs so that I can

cancel this with this I know know that

by looking at this balanced equation

that five moles of oxygen here will

yield four moles of carbon dioxide

absolutely so what now I can cancel this

with this and my end result will be

moles of carbon dioxide which is what

they want so you just multiply 4.25

times 4 divided by 5. so the answer will

be 3.4 moles of carbon dioxide for the

excellent student we'll look here 4.25

how many significant figures three so

let's add a zero to make our answer in

three significant figures I converted

mole into mole Bingo and here's the same

answer in color first you need to

balance the equation next you need to

recognize that this is mole to moles to

a geometry problem which means just one

step and then dimensional analysis I

start with the given which is the number

of moles of oxygen and then set up a

conversion factor moles of oxygen

downstairs and moles of carbon dioxide

upstairs because the answer has to be in

moles of carbon dioxide you can salt up

with bottom you do the math 3.4 at the

zero moles of carbon dioxide Bingo

that's the easiest Stoichiometry problem

let's take it up a notch same equation

here if five moles of oxygen react how

many moles of carbon dioxide should be

formed please pause and try to answer

this yourself are you done let me show

you how most of you answer this you said

let's start with the given which is 5

moles of oxygen and then I multiply this

by I have to put moles of oxygen

downstairs and I know that 5 moles of

oxygen will give me four moles of carbon

dioxide and then you cancel molds of

oxygen with moles of oxygen the five

with the five and your end result is

four moles of carbon dioxide this is

correct however you could have saved a

lot of time by recognizing that this 5

moles of oxygen is already written here

and since my equation is balanced the

answer has to be this 4 moles of carbon

dioxide Bingo if your equation is

balanced the 5 moles of oxygen will

react with this doofus to give you four

moles of carbon dioxide voila chemistry

makes so much sense once you understand

what the flip you're talking about

instead of just memorizing like a

freaking donkey forgive my language just

get excited here is another question a

4.25 moles of oxygen react how many

grams of carbon dioxide could be formed

using the same equation please pause

first order of business bounce the

equation it is balanced second order of

business we need to recognize that this

type of problem is Mole 2 grams it's

small to mass which means two steps okay

let's go to town I start with the given

4.25 moles of oxygen and then I multiply

this by I have to put moles of oxygen

downstairs and I know that 5 moles of

oxygen will yield 4 moles of carbon

dioxide which is right here and then

what I can cancel moles of oxygen with

moles of oxygen but this will give me

the answer in moles of carbon dioxide do

I need the answer in moles of carbon

dioxide no I need the mass of carbon

dioxide grams easy can you convert moles

to grams sure put moles of carbon

dioxide here downstairs and look at your

periodic table one mole of carbon

dioxide has one carbon atom and two

oxygen atoms one carbon atom has 12 AMU

or 12 grams and two oxygen atoms means

two multiplied by 16. then I cancel

moles of carbon dioxide with moles of

carbon dioxide the rest is math history

which will give me the answer in grams

the answer is

149.6 grams of carbon dioxide is this

what they wanted yes but an excellent

student will take a look at this number

three significant figures oh here I have

four well let's make them three how do I

do this well you just take care of the

six so instead of 149 do not make it 149

you make it 150 grams of carbon dioxide

and that's your final answer this is how

to solve mold to mass Stoichiometry

problems same answer in colors I

recognize that this is mole to mass

after balancing the equation I'm ready

to go 4.25 moles of oxygen upstairs put

moles of oxygen downstairs to cancel one

another and then five moles of oxygen

will give me four moles of carbon

dioxide but I'm not done yet because I

want my answer in grams not moles I know

that one mole of carbon dioxide will

contain 1 times 12 which is 12 plus 32

which means 44 grams of carbon dioxide

then I can cancel moles of oxygen with

moles of oxygen and moles of carbon

dioxide with moles of carbon dioxide and

the result will be in grams of carbon

dioxide Bingo let's take it up a notch

here is the same equation but a

different question 50.5 grams of oxygen

react how many moles of water could be

formed please pause and try to solve

this yourself let's talk about this is

my equation balanced yet they want grams

to moles oh so Mass to moles also two

steps now I'm ready let's go to town

50.5 grams of oxygen because I start

with what I have then I put grams of

oxygen downstairs in order to cancel

grams of oxygen with grams of oxygen I

know that one mole of oxygen contains

look at your periodic table two Oxygen

16 and 16. so 32 grams of oxygen okay

how can I cancel moles of oxygen because

if I just go with this I'll get the

answer in moles of oxygen but they want

moles of water easy you put moles of

oxygen here downstairs and you look at

the equation I see here that 5 moles O2

will give me four moles of water amazing

then you cancel moles of oxygen with

moles of oxygen and the end result will

be in moles of water just do the math

and the math will give you

1.26 moles of water is this what they

wanted yes it is three significant

figures three significant figures we're

done the answer in color first balance

the equation second recognize that this

is Mass to mole conversion which means

it's just two steps let's go you start

with what you have grams of oxygen let's

put grams of oxygen downstairs to cancel

one mole of oxygen has 32 grams of

oxygen and then you put the moles of

oxygen downstairs look at the equation

five moles of oxygen will give me four

moles of water cancel cancel cancel and

you get 1.26 moles of water yet another

question same equation different

question if 50.5 grams of oxygen react

how many grams of water could be formed

please pause and try to answer this

first my equation is balanced next grams

to grams so this is Mass to mass

Stoichiometry problem meaning it will

take me three steps to complete oopsie

we can do this folks 50.5 grams O2 I

start with what I have I need to cancel

with grams O2 I know that one mole of

oxygen from the periodic table contains

16 plus 16 which means 32 grams of

oxygen now I can cancel grams of oxygen

with grams of oxygen now what do I need

the answer in moles of oxygen no we

still have two steps left what should I

do next I can cancel moles of oxygen

with moles of oxygen so I put moles O2

here I know from the equation that 5

moles of oxygen will give me four moles

of water so I put the four moles of

water right here cancel the moles of

oxygen with moles of oxygen do I need my

answer in moles of water no I need in

grams of water oh so moles to grams I

can put moles of water down stairs so

that I can cancel it with moles of water

upstairs I know that one mole of water

contains two hydrogens so two times one

gram from the periodic table plus one

oxygen which means one times sixteen two

multiplied by one is two plus sixteen is

eighteen grams of water and then

everything is canceled you just multiply

this number by four you multiply this by

18 over 32 times 5 and we get the answer

of

22.725 grams of water and they want the

answer in grams of water an excellent

student will take a look here 50.5 three

significant figures so I need only three

significant figures which means

22.7 grams of water that's the answer

same answer in color look at the

equation is it balanced yes then

recognize the pattern oh this is Mass to

Mass to a geometry problem which means

three steps you start with what you have

and then I know that grams of oxygen can

be put downstairs one mole of oxygen has

32 grams of oxygen then I can cancel

this with this one mole of oxygen has to

cancel with moles of oxygen I know that

5 moles of oxygen will yield four moles

of water then I can cancel four moles of

water with mole of water how do I do

this I know that one mole of water

contains a 18 grams of water then you

cancel grams of oxygen with grams of

oxygen mole of oxygen mole of oxygen

mole of water mold of water your end

result will be in grams of water and

this is how to perform the most

difficult Stoichiometry question which

is Mass to mass Stoichiometry problem

mold to mole problems just one step mol

to mass or mass to mole two steps each

but Mass to mass is three steps in this

video we learned how to balance the

chemical equation how to figure out the

coefficient of Stoichiometry based on

the balanced chemical equation how to

figure out the mold ratio for example by

relating oxygen from the reactants with

water from the products you can also

relate the two reactants together or two

of the products together then we learned

that in real life most reactions are

limiting reactants Stoichiometry but

today's problem were about ideal

Stoichiometry which means we never ran

out of anything in the next video I'll

show you limiting reactants

Stoichiometry where you will run out of

one of the reactants first and you will

not yield 100 of the products can you

answer the following question if the

average human body contains 25.00 moles

of calcium question one what's the

number of calcium atoms in the average

human body question two what's the

number of moles of calcium in a sample

that has 5.00 times 10 raised to the

24th power atoms of calcium let me know

your answers in the comments and here is

another question here is the equation

what's this stoichiometric amount in

grams of oxygen needed to react with

2.50 grams of aluminum in the

aforementioned equation when it's

balanced let me know your answer in the

comments you'll find the answer key to

these two questions in the next video

where we talk about limiting reactants

to a geometry if you find my videos

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