Measuring Amounts (Moles & Volume of Gas)

C3 topic 4 edexcel from CGP book

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Measuring Amounts (Moles)

Knowing the number of moles of something is important to see how much raw material you need for a reaction

1 Mole is the same as the atomic mass of an element

Mass= Mr x Moles

Q. How many moles are there in 66g of CO2 (C=12, 0=16)

A.

1)Rearrange formula   Moles= mass/mr  

2)Put numbers into formula  66/44 = 1.5 moles 

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Measuring amounts (Volume of gas)

 

One mole of any gas occupies 24 dm3

Volume of gas = (Mass/Mr) x 24

So Volume = Moles x 24

Q. Find the volume of carbon dioxide produced (at room T and P) when 2.7g of carbon is completely burned oxygen. (C=12, O=16)

A.

1) Write out the equation  C + O2 --> CO2

2) Find the amount of moles for Carbon m=mass/mr  2.7/12 = 0.225

3) Ratio of C:CO2 is 1:1 so mole number is the same. So you put 0.225 into the equation    0.225 x 24 = 5.4dm3

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Comments

Willow Woodward

in measuring amounts (volume of gas), why is the ratio of C:CO2 1:1.. thats the only bit i don't understand 

Jodie Randell

Because the number of moles of carbon and carbon dioxide is the same. It the equation would of been 2C + O2 ---> CO2 + C- Then the ratio between carbon and carbon dioxide would be 2:1 as there is 2 x as many moles in 2C than there is in the CO2. 

Jodie Randell

Because the number of moles of carbon and carbon dioxide is the same. It the equation would of been 2C + O2 ---> CO2 + C- Then the ratio between carbon and carbon dioxide would be 2:1 as there is 2 x as many moles in 2C than there is in the CO2. 

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