Calculating Mole Grade 10 | Part 1

Summary

This chemistry lesson focuses on calculating moles using the formula n = m/M, where n is the number of moles, m is the given mass, and M is the molar mass. Examples are provided for CO2, H2O, and H2SO4 to demonstrate how to find moles from mass and vice versa. The instructor also introduces a triangle method to rearrange the formula for different calculations, including determining mass from moles and molar mass.

Takeaways

• 🔍 The formula n = m/M is used to calculate the number of moles (n), where m is the given mass and M is the molar mass.
• 📚 The molar mass (M) is the mass of one mole of a substance, which can be found on the periodic table and is measured in grams per mole.
• 🧪 Examples are used to demonstrate how to calculate the number of moles in a given mass of a substance, such as CO2, H2O, and H2SO4.
• 📈 The molar mass of a compound is calculated by summing the atomic masses of all the atoms in the compound's formula.
• ⚖️ For CO2, the molar mass is calculated as 12 (carbon) + 2*16 (oxygen) = 44 grams per mole.
• 💧 For H2O, the molar mass is 2*1 (hydrogen) + 16 (oxygen) = 18 grams per mole.
• 🌊 For H2SO4, the molar mass is 2*1 (hydrogen) + 32 (sulfur) + 4*16 (oxygen) = 98 grams per mole.
• 🔄 The formula can be rearranged to solve for different variables, such as calculating mass when given moles or molar mass.
• 📉 The concept of a 'triangle' is introduced to help remember the relationships and rearrangements of the formula n = m/M.
• 🔢 Practice problems are provided to reinforce learning and apply the formula in various scenarios, including calculating mass from moles and vice versa.

Q & A

What does the formula n = m/M represent?

The formula n = m/M represents the relationship between the number of moles (n), the mass (m), and the molar mass (M) of a substance.

What is the difference between the lowercase 'm' and uppercase 'M' in the context of the formula?

In the formula, the lowercase 'm' represents the given mass of a substance, while the uppercase 'M' represents the molar mass of that substance.

How is the molar mass of CO2 calculated?

The molar mass of CO2 is calculated by adding the atomic mass of one carbon atom (12) and two oxygen atoms (16 each), resulting in a total of 44 grams per mole.

What is the molar mass of H2O?

The molar mass of H2O is calculated by adding the mass of two hydrogen atoms (1 each) and one oxygen atom (16), resulting in a total of 18 grams per mole.

How many moles are in 88 grams of CO2?

Using the formula n = m/M, and knowing the molar mass of CO2 is 44 grams per mole, there are 2 moles in 88 grams of CO2.

What is the molar mass of H2SO4?

The molar mass of H2SO4 is calculated by adding the mass of two hydrogen atoms (1 each), one sulfur atom (32), and four oxygen atoms (16 each), resulting in a total of 98 grams per mole.

How many moles are in 54 grams of H2O?

Using the formula n = m/M, and knowing the molar mass of H2O is 18 grams per mole, there are 3 moles in 54 grams of H2O.

How many moles are in 49 grams of H2SO4?

Using the formula n = m/M, and knowing the molar mass of H2SO4 is 98 grams per mole, there are 0.5 moles in 49 grams of H2SO4.

How can the formula n = m/M be rearranged to solve for mass (m)?

To solve for mass (m), the formula can be rearranged to m = n * M, where n is the number of moles and M is the molar mass.

How can the formula n = m/M be rearranged to solve for molar mass (M)?

To solve for molar mass (M), the formula can be rearranged to M = m/n, where m is the mass and n is the number of moles.

What is the mass of 3 moles of CO2?

Using the rearranged formula m = n * M, and knowing the molar mass of CO2 is 44 grams per mole, the mass of 3 moles of CO2 is 132 grams.

Outlines

00:00

🔬 Chemistry Lesson: Understanding Moles and Molar Mass

This paragraph introduces the concept of moles and molar mass in chemistry. The distinction between lowercase 'm' for mass and uppercase 'M' for molar mass is clarified. The formula n = m / M is introduced, where n represents the number of moles, m is the given mass, and M is the molar mass. The molar mass of CO2 is calculated as an example, highlighting the importance of using the periodic table to find the mass of individual elements (carbon = 12, oxygen = 16) and summing them to find the molar mass of the compound (44 g/mol). The process is repeated for H2O and H2SO4, emphasizing the method of calculating moles from given mass and vice versa.

05:02

📐 Using the Triangle Method to Manipulate Chemical Formulas

The paragraph explains how to use a triangle method to rearrange the formula n = m / M to solve for different variables. It demonstrates how to isolate n, m, or M by manipulating the formula accordingly. The method is applied to calculate the mass of a given number of moles, such as determining the mass of 3 moles of CO2. The molar mass of CO2 is used again (44 g/mol), and the calculation results in 132 grams for 3 moles. The lesson continues with more examples, including calculating the mass of 9 moles of NaOH, where the molar mass is found by adding the atomic masses of sodium (23), oxygen (16), and hydrogen (1), resulting in 40 g/mol.

10:02

🧪 Calculating Moles from Given Mass: An Example with CaCO3

The final paragraph focuses on calculating the number of moles from a given mass, using the formula n = m / M. The example provided is 50 grams of calcium carbonate (CaCO3). The molar mass of CaCO3 is calculated by summing the atomic masses of calcium (40), carbon (12), and three oxygen atoms (3 x 16), resulting in 100 g/mol. Using the formula, the calculation shows that 50 grams of CaCO3 is equivalent to 0.5 moles. This section reinforces the concept of molar mass and its application in determining the quantity of a substance in terms of moles.

Keywords

💡Mole (n)

In the context of the video, 'mole' refers to a fundamental unit in chemistry that represents the amount of a chemical substance. It is used to express quantities of atoms, molecules, or ions. The video emphasizes that 'n' stands for the number of moles, which is a crucial part of the formula n = m/M. The mole concept is used to calculate the number of moles in a given mass of a substance, such as in the example of CO2, where the number of moles is calculated by dividing the given mass (88 grams) by the molar mass (44 grams/mole).

💡Mass (m)

Mass, symbolized by 'm' in the video, is the measure of the amount of matter in an object. It is typically measured in grams and is a key component in the formula used to calculate moles. The video clarifies the difference between 'small m' for given mass and 'capital M' for molar mass. An example provided is calculating the moles of CO2, where the given mass (88 grams) is divided by the molar mass to find the number of moles.

💡Molar Mass (M)

Molar mass, denoted by 'M' in the video, is the mass of one mole of a substance. It is expressed in grams per mole (g/mol) and can be found on the periodic table. The video explains that molar mass is calculated by summing the atomic masses of all the atoms in a molecule, as demonstrated with CO2 (44 g/mol) and H2O (18 g/mol). It is used in the formula n = m/M to find the number of moles.

💡CO2

CO2, or carbon dioxide, is used as a primary example in the video to illustrate the process of calculating moles. It is composed of one carbon atom and two oxygen atoms. The video uses CO2 to demonstrate how to calculate molar mass (44 g/mol) and subsequently the number of moles in a given mass (88 grams), which results in 2 moles.

💡H2O

H2O, or water, is another substance used in the video to explain the concept of moles. The molar mass of water is calculated by adding the atomic masses of two hydrogen atoms (1 g/mol each) and one oxygen atom (16 g/mol), totaling 18 g/mol. The video uses this to calculate the number of moles in 54 grams of water, resulting in 3 moles.

💡Formula

The formula n = m/M is central to the video's theme, illustrating how to calculate the number of moles from a given mass and molar mass. The formula is fundamental to stoichiometry and is used throughout the video with different examples, such as CO2, H2O, and H2SO4, to demonstrate its application.

💡Periodic Table

The periodic table is referenced as the source for atomic masses needed to calculate molar masses. The video mentions looking up carbon, oxygen, hydrogen, and sulfur on the periodic table to find their respective atomic masses, which are then used in calculations for moles.

💡Atomic Mass

Atomic mass, as discussed in the video, is the mass of a single atom of an element. It is used to calculate the molar mass of compounds by summing the atomic masses of all atoms in the molecule. For example, the atomic masses of carbon (12) and oxygen (16) are used to find the molar mass of CO2.

💡Mole Concept

The mole concept is a fundamental idea in chemistry that allows for the measurement of substances in terms of their number of particles (atoms, molecules, ions). The video uses the mole concept to explain how to convert between mass and the number of moles using molar mass.

💡Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. While not explicitly named in the video, the concept is central to the calculations being performed. The video demonstrates basic stoichiometry through the calculation of moles from mass and vice versa.

💡Example Problems

Example problems are used throughout the video to illustrate the concepts being taught. These include calculating moles from mass for CO2, H2O, and H2SO4, as well as calculating mass from moles for CO2 and NaOH. The examples serve to reinforce the understanding of the formula n = m/M and its application.

Highlights

Introduction to the formula n = m/M, where n stands for moles, m for mass, and M for molar mass.

Explanation of the difference between lowercase 'm' for mass and uppercase 'M' for molar mass.

Molar mass is the mass of a substance per mole, measured in grams per mole.

Example calculation of moles in 88 grams of CO2 using the formula n = m/M.

Calculation of molar mass for CO2 as 44 grams per mole.

Explanation of how to calculate moles when given mass and molar mass.

Example calculation of moles in 54 grams of H2O using the formula n = m/M.

Calculation of molar mass for H2O as 18 grams per mole.

Example calculation of moles in 49 grams of H2SO4 using the formula n = m/M.

Calculation of molar mass for H2SO4 as 98 grams per mole.

Introduction to the concept of using a triangle to rearrange the formula for different calculations.

Explanation of how to calculate mass when given moles and molar mass.

Example calculation of mass in three moles of CO2.

Calculation of mass for three moles of CO2 as 132 grams.

Example calculation of mass for nine moles of NaOH.

Calculation of molar mass for NaOH as 40 grams per mole.

Example calculation of moles in 50 grams of CaCO3.

Calculation of molar mass for CaCO3 as 100 grams per mole.

Final example calculation of moles in 50 grams of CaCO3 resulting in 0.5 moles.

Transcripts

hey guys hope you're well so this lesson

is all going to be about this formula

over here so the n stands for mole the

now you see there's a small M and

there's a capital M don't confuse those

okay so the small m is the mass

or let's say the given Mass okay this

will all make sense when we do some

examples that's the given mass and then

the capital M is called

molar mass

okay and what that is is it's the mass

on the periodic

table

and it's measured in grams

per mole so you write it like that okay

this will make sense as we do some

examples so what I want us to do now is

answer the following question

so this question says how many moles are

there in 88 grams of CO2 okay now by the

way this given mass is also measured in

grams so what we can do is we use this

formula over here okay so we set n

equals to M over capital M now look how

easy this is they gave us 88 grams so

that is the small M the small m is the

given mass and so you're going to say 88

over now to calculate this part over

here this is the mass on the periodic

table so if you look at CO2 well what we

can see is that that is going to be one

carbon atom okay so it's one carbon atom

plus and then there's two oxygens over

here so two oxygens okay and so that

would be one carbon atom which has a

mass of 12. and then two oxygens would

now oxygen has a mass of 16.

so if you work this out correctly you

should get 44.

and then remember that the units of

capital M would be

um

grams per mole so you're going to say

grams per mole and so you're gonna go

put that number down here at the bottom

and then if you had to calculate this

you're going to end up with two

mole

so here's another example and then as we

go along in this lesson I'm going to

give you more questions like this but

then I'm also going to start changing

the questions up where you're going to

have to start using this formula in

different ways

so it says how many moles are there in

54 grams of H2O okay so we're going to

say n equals to M over capital M now

remember that the small m is the given

Mass

the Big M is the molar mass

which is from the periodic table

and then n is the mole so we're going to

say uh n is equal to another given mass

is 54. that's what they gave us 54.

now the molar mass you have to go get

that on the periodic table so this is

H2O so that means

um the the molar mass of H2O would be

there's two hydrogens there's two

hydrogens

and there is one oxygen one oxygen and

so the mass of that would be 2

multiplied by one

plus 1 multiplied by oxygen which is 16.

and if you had to work that out you

would get 18 and then the the units is

grams per mole so I need to say I need

to say 18 grams per mole so I put a 18

over there and if you had to go work

this out you'd end up with three mole

here's another one so how many moles are

there in 49 grams of h2so4 okay so we

know that to calculate moles you're

going to say n equals to M over capital

M now remember small m is the given Mass

which must always be measured in grams

and then the capital M is the molar mass

which is the mass that you get on the

periodic table

and then n is the mole okay so the given

mass is 49.

now h2so4 so what that is is

um to work out the molar mass of h2so4

well there is

um two hydrogens so two hydrogens there

is one sulfur atom okay so let's just

write that a bit better one sulfur atom

and four oxygen atoms four oxygens and

so to work out the mass that would be

two times one because each hydrogen has

a mass of one

um one multiplied by sulfur's mass which

is 32 and then four oxygens each oxygen

has a mass of Sixteen and if you had to

go calculate that

you end up with 98 now the units of that

is grams per mole so you could put 98

over there and if you had to go

calculate that you're going to get 0

comma five

Mo now in the next questions I'm going

to show you um the next question coming

up after this one how to change this

formula and use it in different ways

okay so let's do that

so what we can do is we can make a

triangle so you know the triangles that

I've showed you in previous chapters

like maybe in electricity we've got

these triangles where we've got a v i r

or maybe you've seen other ones like WV

and Q or maybe you've seen uh q i and T

for example now when we have triangles

like that it makes it easier to work

with them okay and to do different

things so here you see this one's at the

top so the one that's at the top is

always the top part of the triangle okay

and then the other two you could just

put at the bottom so the end you could

put there and then the capital M you

could put there so now

you could make a whole bunch of

different formulas let's say you're

trying to get this one by itself

well

we know that if that one's at the top

then the other two at the bottom are

next to each other so you would multiply

them like that okay or maybe

you want to get this one by itself well

that one you wouldn't really need to get

because that one's the one that's on the

periodic table okay but let's just say

maybe they gave you a weird question uh

where oh no I don't think they'll do

that so don't worry about that one and

then obviously to work out this one over

here

oh no let me actually go back to this

one they could sometimes do something

weird where they give you like a made-up

molecule that is not on the periodic

table

and then they ask you to calculate this

part

well to do that you'll just say

um this is at the top and this is at the

bottom so that's at the top that's at

the bottom and then lastly

if we need to calculate this one well we

know how to do that one already because

this m is at the top

and then the Big M is at the bottom and

then you just get back to this formula

over here okay so you need to know how

to use all three of these and so for the

remainder of this lesson I'm going to

give you some questions

um that's going to help you practice the

different types

so here's our next question so it says

determine the mass

in three moles of CO2 okay so we know

that we've got these formulas okay now

we know that n stands for mole the small

m stands for mass or given Mass if they

give you a mass and then capital M is

the molar mass

now remember that the molar mass is the

one that is on the periodic table so

they want us to calculate

the the the mass

not the molar mass that just means the

normal Mass so that's this one okay so

we need to get a formula with this one

and so that's over here

and so we could say that that mass is

equal to the number of moles multiplied

by the molar mass so that's going to be

equal to 3 because they said there's

three moles multiplied now the molar

mass is from the periodic table so to

calculate the molar mass of CO2

well there is going to be one carbon

atom one carbon atom and then there's

going to be two oxygen atoms so the mass

would be 1 times 12.

plus 2 times the mass of oxygen which is

16 and that's going to give you 44 grams

per mole so you can put 44 of here and

if you had to go work that out

you would end up with 132 grams

oh just like that yeah you're just going

to say 132 grams you're not going to say

grams per mole the only time you say

grams per moles when you're working out

the capital M which we've just done here

on the periodic table so for this one

you just say grams okay let's do some

more examples

this one says determine the mass of 9

mole of NaOH so if we have our triangle

over here

then if they want us to calculate mass

well that's this one over here so that's

going to be n multiplied by capital M

okay so we're going to use that formula

and so the number of moles is nine

and then to get the

um to get the sorry you need to get the

mass on the periodic table so n

a whoopsie why am I writing so weird n a

o h well that's going to be 1 in a atom

you can see one in a plus one oxygen

plus one hydrogen plus one hydrogen and

so that's going to be the mass of n a 23

the mass of oxygen 16 and the mass of

hydrogen is one so that's going to be 40

grams

per mole and so we could say 9 times 40

and that's going to be 360 grams

here's our last question so it says how

many moles are there in 50 grams of

CaCO3 okay so if we have that triangle

then they want the number of moles now

so they want this so number of moles is

equal to whatever's at the top divided

by the capital M which is molar mass

so they remember that n is Mo

m is the given Mass

and here they've given it to us and then

capital M is the molar mass molar mass

which is on the periodic table periodic

table so we're going to say n equals to

M over capital M and so the mass is

going to be 50.

to go work out the molar mass of calcium

carbonate or CaCO3

then that's going to be one calcium atom

one calcium

plus one carbon

plus three oxygens

okay and so that's going to be one

calcium which is 40 grams

per mole plus one carbon which is 12.

plus three oxygens now each oxygen is

16. so if you had to go calculate this

you get a hundred

grams

per mole so that's going to be over a

hundred and so if you had to go work

this out you're going to end up with

zero comma five

mole