Moles

Question 1

What is a mole?

Answer 1

One mole of any substance has the same number if atoms, molecules or ions. This is called Avogadro’s constant. It is 6.02x10²³ per mole. One mole is the relative atomic mass of any substance in grams. E.g. 12g of carbon is one mole because carbon has a relative atomic mass of 12.

Question 2

What is the equation for number of moles?

Answer 2

Moles = Mass(g) / Mr
Mr = Relative formula mass

Question 3

How do you calculate the mass of reactants or products using moles?
CH4 + 2O2 = CO2 + 2H2O

“If we burn 5g of methane in oxygen, how much carbon dioxide would we produce?”

Answer 3

You use the ratio as moles. E.g.
CH4 + 2O2 = CO2 + 2H2O

If we burn 5g of methane in oxygen, how much carbon dioxide would we produce?

Methane and carbon dioxide are mentioned so you only look at those.

CH4
Mass = 5g
Mr = 12 + 4 = 16
Moles = 5/16 = 0.3125mol

The way that you figure out the mass, mr and moles of carbon dioxide is that you look at methane and carbon dioxide in the equation, you can see that we have one of each so it is a one to one ratio so the moles would be the same. And then you work backwords.

CO2
Mass = Mol x Mr = 0.3125 x 44 = 13.75 grams
Mr = 12 + 32 = 44
Moles = 0.3125

Question 4

When working out the ratio what should you ignore?

Answer 4

You should ignore all the small numbers and focus on the big numbers as they show the number of moles.

Question 5

What should you ignore when figuring out the relative formula mass?

Answer 5

Ignore the big numbers only/

Question 6

What is this question asking you?

“Interpret the balanced equation in terms of the ratio of moles.”?

Answer 6

It is basically asking for the ratio of the substances compared to each other. So your answer is going to be a ratio.