To produce 20 moles of ammonia via Haber's process, how many moles of hydrogen molecules are required?

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g of magnesium oxide.
The percentage purity of magnesium carbonate in the sample will be: 
(Atomic weight of Mg=24)

10 g of hydrogen and 64 of oxygen were filled in a steel vessel and exploded. The amount of water produced in this reaction will be:

1. 2 mol

2. 3 mol

3. 4 mol

4. 1 mol

The moles of lead (II) chloride that will be formed from a reaction
between 6.5 g of PbO and 3.2 g of HCl are:

1. 0.044
2. 0.333
3. 0.011
4. 0.029

In the Haber process, 30 litres of dihydrogen and 30 litres of dinitrogen were taken for the reaction which yielded only 50% of the expected product. What will be the composition of a gaseous mixture under the above condition in the end:

$4N{H}_3$ $+$ $5O_2$ $\to$ $6H_{2}O$ $$ $+$ $4NO$

When one mole ammonia and one mole oxygen are taken:
1.  Oxygen is completely consumed
2.  Ammonia is completely consumed
3.  Both (1) and (2) are correct
4.  None of the above options is correct