Calculating mass or volume of a substance from a chemical equation

Here might be a little difficult for you, but I would say, Don't give up!!!
e.g. When 4g of Magnesium reacts in oxygen gas, magnesium oxide will be produced. Calculate the mass of magnesium oxide produced?
[Mg=24, O=16]
Firstly, you have to write out the equation....
Mg + O2 --> MgO
Next, check if the equation is balanced or not... Looks like it is not balance.. so, BALANCE it now!
you should get...
2Mg + O2 --> 2MgO
Now we can start our calculation... given is 4g of magnesium... so we need to calculate the mole value for Magnesium...
Mole = Mass / RAM or RMM
mole = 4g/24 and you'll get 0.1667 mole
Now you have to refer to your balanced equation...
2 mole of Magnesium will produce 2 mole of Magnesium Oxide
therefore, 0.1667 mole of Mg will also produce 0.1667 mole of MgO
The final step now is to convert the mole value of MgO to mass...
mole = mass / RAM or RMM
so,
Mass= mole X RAM or RMM
= 0.1667 X [24 + 16]
= 0.1667 X 40
= 6.6667g
= 6.67g
** leave your answer in 2 decimal places...
Q: What is the mass of copper oxide that will be needed to produce copper when it is reacted with hydrogen gas?
[Cu=64, H=1, O=16]