[Felicity.L]

Hi, I was doing a couple of questions that I have a feeling I did wrong, but don't know the correct format to do it in. Can anybody where I went wrong and what I should do instead? Thanks. 

1) How much copper (1) chloride can be produced beginning with 75.0g of copper (1) oxide?
Cu₂O + 2HCL --> 2CuCl + H₂O

What I did:

Required/Given
2(99)/147 x 75g
=101g

However, the answer key said 104g

2) What volume of oxygen gas is produced the decomposition of 100.0 g of sodium nitrate?
2NaNO₃--> 2NaNO₂+O₂
32/2(84.99) x 100
= 18.83g

Answer key: 13.2g

Any help would be appreciated. Thanks!

[Borek]

2(99)/147 x 75g

What is 147?

Answer key: 13.2g

Since when grams are used to measure volume?