The Ideal Gas equation | A level Chemistry

Summary

This chemistry video tutorial delves into the ideal gas equation, a fundamental concept in A-Level chemistry. It explains the equation's derivation through everyday examples like party balloons, illustrating how gas behavior relates to temperature (Charles's Law), pressure (Boyle's Law), and the number of gas molecules. The video meticulously covers unit conversions crucial for using the equation correctly, such as converting Pascals, cubic meters, and Kelvin. It also guides through solving practical problems using the ideal gas equation, including calculating moles of gas and applying it to chemical reactions, ensuring a comprehensive understanding of this essential chemistry topic.

Takeaways

• 🎈 The ideal gas equation, PV=nRT, is derived from observing how gases behave under different conditions, such as temperature and pressure changes.
• 🔍 Charles's Law states that the volume of a gas is directly proportional to its temperature (V∝T).
• 📉 Boyle's Law indicates that the pressure of a gas is inversely proportional to its volume (P∝1/V) when temperature is constant.
• 🌡️ The number of moles of a gas is directly proportional to the volume it occupies, which is a fundamental concept in the ideal gas law.
• 📐 The ideal gas equation is applicable to all gases under ideal conditions, regardless of the type of gas.
• ⚖️ The units for the ideal gas equation are crucial: pressure (Pascals), volume (cubic meters), moles (moles), temperature (Kelvin), and the gas constant (8.31 J/K/mol).
• 🔄 Understanding unit conversions is vital for correctly applying the ideal gas equation, especially between Kelvin and Celsius, and cubic meters with other volume units.
• 🔢 The ideal gas equation can be rearranged to solve for different variables, such as pressure, volume, or the number of moles.
• 🧪 Practical applications of the ideal gas equation include calculating moles of gases in reactions, determining temperatures in chemical processes, and finding the molar mass of volatile liquids.
• 🔄 The ideal gas equation can be combined with chemical equations to perform stoichiometric calculations and find the amounts of reactants or products in chemical reactions.

Q & A

What is the ideal gas equation?

The ideal gas equation is PV = nRT, where P is the pressure, V is the volume, n is the number of moles of gas, R is the gas constant, and T is the temperature in Kelvin.

What is Charles's law as mentioned in the script?

Charles's law states that the volume of a gas is proportional to its temperature, when the pressure is held constant.

What is Boyle's law and how does it relate to the volume of a gas?

Boyle's law states that the pressure of a gas is inversely proportional to its volume, provided the temperature and the amount of gas remain constant.

How does the number of moles of gas affect its volume according to the script?

The volume of a gas is directly proportional to the number of moles of gas it contains, assuming the temperature and pressure are constant.

What does the ideal gas equation assume about the behavior of gases?

The ideal gas equation assumes that all gases behave in the same ideal way, regardless of their composition, obeying the rules of direct or inverse proportionality with volume, pressure, and temperature.

What is the value of the gas constant R in the ideal gas equation?

The gas constant R in the ideal gas equation is 8.31 joules per Kelvin per mole.

How can you convert pressure from kilopascals to pascals?

To convert pressure from kilopascals to pascals, you multiply by 1,000 (since 1 kilopascal is equal to 1,000 pascals).

What is the Kelvin temperature scale and how does it relate to the Celsius scale?

The Kelvin scale is a temperature scale that starts at absolute zero (0 K) and increases by the same amount as the Celsius scale. To convert Celsius to Kelvin, you add 273.15.

How do you convert cubic centimeters to cubic meters?

To convert cubic centimeters to cubic meters, you divide by one million, because one cubic meter is equal to one million cubic centimeters.

What is the significance of the units used in the ideal gas equation?

The units used in the ideal gas equation (Pascals for pressure, cubic meters for volume, Kelvin for temperature) are significant because they ensure the equation's balance and allow for accurate calculations of gas properties.

How can the ideal gas equation be rearranged to solve for different variables?

The ideal gas equation can be rearranged algebraically to solve for different variables such as pressure (P = nRT/V), volume (V = nRT/P), temperature (T = PV/nR), and the number of moles (n = PV/RT).

Outlines

00:00

🎈 Introduction to the Ideal Gas Equation

This paragraph introduces the Ideal Gas Equation, a fundamental concept in A-Level Chemistry, specifically in the chapter on the amount of substance. The origin of the equation is explained through a relatable example involving party balloons and their behavior under different conditions. The script discusses how balloons expand in warm environments due to increased temperature (Charles's Law), contract when cooled (inversely related to volume), and increase in volume when more gas is added (directly related to the number of moles). These observations lead to the formulation of the Ideal Gas Equation: PV=nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature in Kelvin. The importance of memorizing this equation for exams is emphasized, along with understanding the units for each variable.

05:02

🔍 Understanding Units in the Ideal Gas Equation

This section delves into the units used in the Ideal Gas Equation, focusing on pressure in Pascals (Pa), volume in cubic meters (m³), and temperature in Kelvin (K). The script clarifies common unit conversions, such as kiloPascals to Pascals and the conversion between Celsius and Kelvin scales. It also addresses the less familiar unit of volume, cubic meters, and provides conversions to more commonly used units like cubic centimeters and cubic decimeters. The goal is to ensure that students can comfortably work with the units required for the Ideal Gas Equation in various exam scenarios.

10:05

🧪 Manipulating the Ideal Gas Equation

The script explains how to manipulate the Ideal Gas Equation to solve for different variables, such as pressure, volume, or the number of moles. It emphasizes the importance of rearranging the equation to isolate the desired variable and then substituting the known values. The process involves converting all quantities to their SI units before solving. An example calculation for the number of moles of oxygen gas is provided, demonstrating the step-by-step approach, including unit conversions and the final calculation.

15:06

🔬 Applications of the Ideal Gas Equation

This part of the script explores practical applications of the Ideal Gas Equation, such as determining the molar mass (M R) of a volatile liquid. The process involves measuring the volume of gas produced when a liquid evaporates and the mass loss of the liquid container. The Ideal Gas Equation is used to calculate the number of moles of the gas, which then allows for the calculation of the M R. The script also discusses how the Ideal Gas Equation can be combined with chemical equations to perform stoichiometric calculations, such as determining the number of moles of reactants or products based on the gas laws.

20:09

📚 Advanced Problems Using the Ideal Gas Equation

The final paragraph presents more complex problems that involve using the Ideal Gas Equation to find the volume of gases produced in chemical reactions. It covers scenarios where the reaction conditions (temperature and pressure) are given, and the task is to calculate the volume of gas produced from a known mass of a reactant. The script demonstrates how to use the Ideal Gas Equation to find the number of moles of a gas, and then how to use stoichiometry to find the volume of another gas in the reaction. This section showcases the application of the Ideal Gas Equation in solving multi-step chemical problems.

Keywords

💡Ideal Gas Equation

The Ideal Gas Equation is a fundamental concept in chemistry that describes the behavior of an ideal gas. It is represented as PV=nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin. The video uses this equation to explain how gases behave under different conditions, such as changes in temperature and pressure. The Ideal Gas Equation is central to the video's theme as it serves as the basis for understanding gas behavior.

💡Charles's Law

Charles's Law states that the volume of a gas is proportional to its temperature, provided the pressure and the amount of gas are held constant. This law is named after Jacques Charles and is demonstrated in the video through the example of balloons expanding in a warm environment and shrinking in a cold one. It is a key component of the Ideal Gas Equation and helps to establish the relationship between temperature and volume.

💡Boyle's Law

Boyle's Law explains the inverse relationship between the pressure and volume of a gas when the temperature and the amount of gas are constant. If the pressure increases, the volume decreases, and vice versa. The video illustrates this by squeezing a balloon, showing that applying pressure reduces its volume. This law is essential for understanding how pressure affects the size of a gas container.

💡Moles

Moles are a measure used in chemistry to express quantities of a chemical substance, defined as the number of particles in a substance divided by the number of particles in 12 grams of carbon-12. In the context of the video, the number of moles (n) is a variable in the Ideal Gas Equation and is directly proportional to the volume of a gas. The video uses the concept of adding more air to a balloon to explain how an increase in moles leads to an increase in volume.

💡Pascal

Pascal is the SI unit of pressure, named after the French mathematician and physicist Blaise Pascal. The video mentions Pascal in the context of expressing pressure measurements in the Ideal Gas Equation. It also discusses the conversion between different units of pressure, such as kilopascals to pascals, which is important for using the Ideal Gas Equation correctly in calculations.

💡Kelvin

Kelvin is the base unit of temperature in the International System of Units (SI) and is one of the seven base units. The video explains that temperature in the Ideal Gas Equation must be expressed in Kelvin, not in degrees Celsius. It provides a method for converting degrees Celsius to Kelvin by adding 273, which is crucial for accurately using the Ideal Gas Equation.

💡Gas Constant (R)

The Gas Constant (R) is a fundamental constant in the kinetic theory of gases, commonly used in the Ideal Gas Law. It is the same for all gases and has a value of 8.314 J/(mol·K). The video emphasizes the importance of remembering this constant for solving problems using the Ideal Gas Equation, as it relates the energy of a gas to its temperature and the amount of substance.

💡Unit Conversions

Unit Conversions are discussed in the video as an essential skill when working with the Ideal Gas Equation. The video provides examples of converting pressure from kilopascals to pascals and volume from cubic centimeters to cubic meters. Understanding these conversions is necessary for ensuring that all variables in the equation are expressed in the correct SI units.

💡Volume

Volume in the context of the video refers to the amount of space occupied by a gas, which is a variable in the Ideal Gas Equation. The video explains that volume is typically measured in cubic meters and provides conversions to other units like cubic centimeters. The concept is used to demonstrate how the volume of a gas changes with temperature and pressure.

💡Molar Mass

Molar Mass is the mass of one mole of a substance and is used in the video to calculate the number of moles of a gas. It is an important concept when relating mass to the number of moles using the Ideal Gas Equation. The video demonstrates how to use the molar mass to find the moles of a gas, which is then used to calculate other properties like volume.

💡Chemical Reactions

Chemical Reactions are discussed in the video in relation to how they can be analyzed using the Ideal Gas Equation. The video provides an example of octane burning in air to produce carbon dioxide and water, and how to calculate the number of moles of carbon dioxide produced. This illustrates how the Ideal Gas Equation can be applied to real-world chemical processes.

Highlights

Introduction to the ideal gas equation in A-Level Chemistry

Explaining the origin of the ideal gas equation using party balloons

Charles's law: Volume of a gas is proportional to temperature

Boyle's law: Pressure is inversely proportional to volume

Volume is proportional to the number of moles of gas

Combining relationships to form the ideal gas equation PV=NRT

Importance of remembering the ideal gas equation for exams

Units for each quantity in the ideal gas equation

Conversion of pressure units from kilopascals to pascals

Understanding Kelvin scale and its conversion from Celsius

Volume units in cubic meters and their conversions

Rearrange the ideal gas equation to solve for different variables

Calculating the number of moles of oxygen gas using the ideal gas equation

Determining the temperature in degrees Celsius using the ideal gas equation

Using the ideal gas equation to find the molar mass of a volatile liquid

Combining the ideal gas equation with chemical equations for combustion reactions

Calculating the total volume of gas produced from a cracking reaction

Transcripts

hello everybody and welcome to this a

level chemistry video about the ideal

gas equation this is one of these sub

topics in the amount of substance

chapter 4 a level chemistry and in this

video we'll look briefly at the origin

of the ideal gas equation we'll look in

depth at how you use the ideal gas

equation including unit conversions and

then we'll finish by looking at how we

can work with gases in equations

including a couple of questions to that

effect the origin of the ideal gas

equation can be explained using a simple

example of party balloons if we take a

number of identical party balloons with

an identical number of molecules of air

inside them we can subject these

balloons to different conditions and see

how they behave and their behavior

allows us to come up with some

scientific rules that form the ideal gas

equation first of all if we place a

party balloon in a warm environment say

a boiler cupboard then the party

balloons will expand and then they might

pop you can see this same effect if

people have put party balloons outside

their house for somebody's birthday and

it's a hot day and the balloons will pop

in the same way but the opposite way

around if you took a party balloon and

put it inside a freezer that party

balloon would shrivel up maybe not go

shrivel down to nothing but it would

definitely get smaller and what this

allows us to realize is that the volume

of space a gas occupies the gas inside

the balloon is proportional to the

temperature of those gasses so the

volume V is proportional to the

temperature T and this is actually known

as Charles's law after one of the

scientists who did a lot of work in this

area if we took another party balloon

and we just simply squeezed it as we've

all done probably when we were younger

we can say that that party balloon

assuming that we're squeezing it and

stopping it moving out from between our

fingers

that party balloons actually going to

get smaller and what that means is that

the pressure that we exert on gases is

influencing the volume and the pressure

is inversely proportional to the volume

what that means is if we increase the

pressure the volume gets smaller and so

this is Boyle's law pressure is

inversely proportional to the volume and

then last of all if we were to carefully

undo the knot in the balloon and breathe

out more air into that balloon we would

find that the balloon of course would

get larger the volume would increase and

what that means is we've put more

molecules of gas into the balloon more

moles and so the volume of that balloon

is increasing because volume is

proportional to the number of moles of

gas inside the balloon and this these

three relationships that we've got here

on the slide that combine together to

give us the ideal gas equation and it's

called the ideal gas equation because

all gases are assumed to behave in this

same ideal way regardless of whether

they're carbon dioxide or oxygen or

nitrogen they all obey these rules where

their volume is proportional to a number

of different factors so this is the

ideal gas equation PV equals NRT it's

got quite a nice rhythm to it when you

say it like that you need to remember

this so you can use it in exam questions

because it won't be given to you and

you'll get a mark for remembering it not

only do you need to remember it you need

to be able to understand it and use it

including understanding the units for

each of these quantities so P is

pressure and that's measured in Pascal's

and Pascal's is the international symbol

international unit for pressure V is

volume measured in cubic meters n stands

the number of moles T is the temperature

measured in Kelvin which has got a

symbol K and last of all R is the gas

constant and it's got a number 8.31

joules per Kelvin per mole and you need

to remember those numbers 8.31 because

that is a constant which means that

whatever the gas is it will always have

that many joules of energy per Kelvin

per mole that means if you've got one

mole of a substance at 20 Kelvin it will

have 8.31 times by 20 that's how much

energy that gas will have let's move

back to the units Pascal's cubic meters

and kelvins probably not units that we

use frequently so let's have a look at

each of those now let's start with our

units by looking at pressure in Pascal's

in exam questions they like to try and

trip you up by giving you the units in

something that is not the SI form not

the standard way of giving it to you so

they might give it to you in kiloPascals

and if that's the case well that's

really lovely because they might give

you a pressure of 3 kilo Pascal's which

to convert into Pascal's you simply

multiply by a thousand in the same way

that three thousand grams is three

kilograms or three kilograms is three

thousand grams so that's nice

atmospheric pressure is taken to be 101

kiloPascals so they might talk to you

about atmospheric pressure that would be

a bit mean expecting you to remember 101

kiloPascals but that is atmospheric

pressure sometimes approximated to 100

kilo Pascal's so to convert killer

Pascal's into Pascal's you just simply

multiply by 1,000 now temperature

temperature is in Kelvin and that is an

entirely new temperature scale named

after a scientist Lord Kelvin who

all sorts of crazy experiments in his

country house but essentially the Kelvin

scale is a recalibrated degrees Celsius

scale that starts at zero you might have

wondered why we have a temperature scale

that goes negative wouldn't it be easier

if we have one that starts at zero and

that's what the Kelvin scale does it

starts at zero and that is referred to

as absolute zero that is as cold as it

is theoretically possible to get we've

got below 1 Kelvin

I believe but never down to zero it's a

theoretical temperature now the good

news for you and your exams is it's not

a really tricky conversion to work

between degrees Celsius and Kelvin zero

degrees Kelvin is minus 273 degrees

Celsius 20 Kelvin is minus 253 degrees

Celsius so you can see that what we're

doing is we're adding 273 on to the

degree Celsius scale to get us into our

kelvin scale so zero degrees Celsius is

273 Kelvin 50 Celsius is 323 Kelvin and

so the scale is nice that's plus 273 or

minus 273 depending on which way you're

converting most likely you'll be adding

273 to convert into Kelvin but what's

really nice is that that increase of one

degree Celsius from say 50 to 51 is the

same as one Kelvin from three to three

to three to four so these first two

conversions aren't too bad let's take a

look at volume volume is usually taken

to be the trickiest one now the units of

volume for the ideal gas equation are in

meters cubed and a cubic metre is

actually really quite big and the reason

that we have these big volumes is

because gases occupy a lot of space now

you can just accept that the volume is

in cubic meters and you can also accept

the conversions so I'll start with the

conversions to convert to be centimeters

which is quite common through given a

volume in cubic centimeters into cubic

meters you divide by a million and

that's because a cubic centimeter is

tiny compared to a cubic meter so a

beaker that holds 500 cubic centimeters

of volume would actually only be 5 times

10 to the minus 4 cubic meters with the

volume so centimeters cubed 2 meters

cubed you divide by a million and then

centimeters cubed to decimeters cubed

you divide by 1,000 the origin of that

can be explained using cubes here we've

got a cube which I will take to be one

meter by one meter by one meter so that

is one cubic meter now a decimeter is

1/10 of a meter so this 1 meter

dimension here is actually 10 decimeters

and so is this one and so it's this one

so the volume is 10 by 10 by 10 which is

1,000 cubic decimeters so one cubic

meter is 1000 cubic decimeters but we

also know that one meter is 100

centimeters so this dimension could also

be referred to as 100 centimeters and

this one 100 centimeters of this one 100

centimeters as well so the volume in

cubic centimeters we is 100 times 100

times 100 so a million and that's the

origin of these conversions cm cubed 2

meters cubed we multiply by 10 to the

minus 6 or divide by a million DM cubed

into meters cubed we divide by a

thousand and it's the opposite going the

other way

so those are the really important

conversions to remember let's get back

to the ideal gas equation itself PV

equals NRT and let's explore the

different forms of this equation because

you might be asked to work out P and

then you need to have an equation where

P equals something so you might prefer

to write that equation and then

substitute numbers into it and then

rearrange numbers people often find that

easier and so that would be possibly

what I recommend remember what the units

are

then alternatively you could use algebra

as your method so PV equals NRT if I've

been asked to work out what P is I need

to divide both sides of this equation by

V and then the V's on the left hand side

cancel out and we're left with NRT

divided by V and making V the subjects

of the equation works in the exact same

way however if we wanted to work out a

number of moles we would need to divide

both sides of the equation by RT and

then the RT would cancel on the right

hand side and would be left with PV

divided by RT equals N and so that's the

rearranging of the ideal gas equation

either by subbing the numbers in at the

beginning or by doing the algebraic

method so let's take a look at a couple

of questions here how many moles are

there in 0.050 cubic meters of oxygen

gas at a temperature of 450 Kelvin and

60,000 Pascal's so the first thing that

I recommend you do is you write the

ideal gas equation out PV equals NRT you

rearrange it to make n the subject N

equals PV over RT and then you write the

quantities V equals T equals P equals

and then you do the conversions because

getting into this routine like this

encourages you to remember to do the

conversions and if you make a slip-up

you're more likely to get method marks

when you say use the wrong volume later

that you've shown that you think it's

the volume whereas if you just use the

wrong volume later without saying what

it is that you're doing you're less

likely to get method marks so convert

each of those quantities like this now

on this occasion no conversions are

necessary because all of the units are

in the correct form but it's a really

good habit to force yourself into then

plug those numbers into the equation you

get your answer and don't forget to put

the unit's in and in this second

question

what was the temperature in degree C of

a gas that has got a pressure of 110,000

Pascal's 0.4 moles of gas occupying a

volume of 1600 cubic centimeters so

again my suggestion is that you write

the ideal gas equation this time with T

as a subject so T equals PV divided by n

R we write down our quantities and then

we take a moment to look at the units

and this time we find out that the

volume is not in the SI units that we

need it's in cubic centimeters so we

need to divide that by a million and get

the correct number of meters cubed so

dividing 1600 by a million we get one

point six times ten to the minus three

cubic meters and so we plug those

numbers into the equation and we get a

temperature now we should note I said

before don't forget to put the unit's

the temperature units are in Kelvin but

this question asked for the temperature

in degrees Celsius so our value in

Kelvin remember is 273 bigger than our

value in degree C would be so we need to

subtract 273 off this to get our

temperature in degrees C so this is our

answer here another application of the

ideal gas equation is that you can use

it to find the M R of a volatile liquid

and to do this what you have is you have

a canister that contains the volatile

liquid and you inject some of it through

a syringe into a second chamber and the

second chamber is inside an oven and

volatile means it turns into a gas

easily and so once the liquid has moved

into the oven it will evaporate and

become a gas and so we can measure the

volume of gas that is produced in this

chamber and we can take a look at what

the mass has dropped by from this

canister

so if the canister lost a certain mass

we will know that that canisters mass

loss is all to do with the fact that the

liquid left through the syringe and into

the oven and then it became a gas whose

volume we measured so let's say that we

collected 1,000 cubic centimeters of gas

inside the oven and that the mass of the

canister began at 30 point-0 grams but

then it dropped and it dropped down to

twenty-five point four two grams and so

we can work out what mass has been

injected and that mass is four point

five eight grams and that four point

five eight grams of the liquid has got a

volume once vaporized of one thousand

cubic centimeters so the first thing

that we need to do to work out what the

M R is is to work out how we're going to

calculate the M R at the end

and since moles equals mass over M R

that means that M R is mass over moles

and so the final calculation that we're

going to do is mass divided by moles to

work out what the mr is and so that

means that the previous step must be to

work out what the moles is because we

know what mass has been lost four point

five eight grams but we don't know the

moles and so we need to use the ideal

gas equation to work out the moles so

that's in the form n equals PV divided

by RT we've got our volume of one

thousand centimeters cubed we need to

convert that into meters cubed by

dividing by a million and we need to

take the temperature of the oven and

that is at only forty four degrees C and

so 44 degrees C we need to convert that

into Kelvin by adding 273 on to it and

then the pressure is 101 kiloPascals

which we then multiply by a thousand to

get one hundred and one thousand

Pascal's we plug those numbers into the

equation

remembering the value for R is eight

point three

and we get a value for our moles we then

take this value of moles and we put it

into the equation down here and we

divide our 4.5 eight grams by the moles

we've just calculated and we get our M R

value you don't normally need to use the

units of M R grams per mole but I like

to put it in because I think it helps

give em our more meaning we're going to

finish this video by taking a look at

how we can combine the ideal gas

equation with other calculations and

with other chemical equations so we've

got a situation here where octane a

hydrocarbon with a molecular formula

c8h18 burns completely in air to give

water and carbon dioxide

there's the chemical equation for it

here we can see the numbers in the

equation nine eight one and one and then

we've been given some data a sample of

octane burns completely in air the

carbon dioxide produced occupies a

volume of twenty thousand cubic

centimeters and has a temperature of 55

degrees C and 101 kiloPascals of

pressure we have to calculate the number

of moles of carbon dioxide present to do

this we need to use the ideal gas

equation PV equals NRT we're going to

rearrange it in the form n equals PV

divided by RT in our data volume is

twenty thousand cubic centimeters which

we need to divide by a million to get

into cubic meters so 0.020

cubic meters the temperature is 55

degrees Celsius which we need to add on

to 73 to get 328 Kelvin and last of all

the pressure is 101 kiloPascals and we

just simply need to multiply that by

1,000 to get one hundred and one

thousand Pascal's of pressure and then

we need to substitute these values into

the calculation and this

final answer of 0.074 1 moles of carbon

dioxide and then there's a follow-up

question asks us to calculate a number

of moles of octane burnt and if we look

at the chemical equation the ratio of

octane to carbon dioxide is 1 octane for

8 carbon dioxide and so to convert the

moles of carbon dioxide into moles of

octane which is what we need to do we

need to divide it by 8 so our answer

from the previous question needs to be

divided by 8 and when we do that we get

9 point 2 6 times 10 to the minus 3

moles of octane and so you can use the

coefficients in the equation those

multipliers to work with moles without

having to use moles mass and M are you

just simply use their proportions from

the multiples in the equation okay we'll

take a look at one last question now a

sample of decane is cracked to produce

butane and ethene as shown in the

equation below and we've got decane on

the left and we've got butane on the

right and three moles of ethene and

that's really important that the decane

produces one mole of butane and three

moles of ici now the reaction is carried

out it's 550 degrees Celsius that's T

and 200 kilo Pascal's so there is P and

our command is if eleven point six grams

of butane are produced what is the total

volume of gas in cubic centimeters

that's so important let's highlight that

now what we need to do first is we need

to go PV equals NRT our final answer

needs to be for the volume so V equals

NRT divided by P which means that we

need to know n RT and P so n is the

number of moles we actually don't have

that yet so that's going to be something

we're going to need to calculate using

the mass R we know is eight point three

one might give it to you

they might not temperature is 550

degrees Celsius which is

823 Kelvin remember we need to add 273 P

is 200 kilo Pascal's which is 200,000

Pascal's now n is the moles of gas and

this is the tricky bit here we've got

two gases we've got ething and we've got

butane and so what we're going to need

to do here is we're going to need to

work out the total moles of gas before

we need to then work out the total

volume of gas and so we've got the mass

of butane 11.6 so mass divided by M R is

moles of butane and the moles of butane

is therefore eleven point six divided by

58 which is the M R of butane which

gives us an answer of not 0.2 moles so

this is how many moles of butane we've

got then we need to look up at the

equation and the ratio is one to three

so we forgot to not point to moles of

butane we will have naught point six

moles of ethene because it needs to be

three times as big and so therefore the

total moles is 0.8 and so this now can

be plugged in for our value of N and so

to finish off we need to calculate not

0.8 times by 8.3 1 times by 8 - 3

divided by 200,000 which comes out at

0.027 for cubic meters and that's not

quite our final answer because they

asked for it in cubic centimeters so now

we need to multiply that by a million

and we've got 27,400

cubic centimeters and so that's the end

of this question we've got our final

answer there this would probably be a

four or five mark question at the very

least ok that's the end of this ideal

gas equation run through hope it was

useful I'll see you next time