​I have a few questions from my homework and I was wondering if I can get some help ​

1. In the chemical reaction between aqueous magnesium chloride and sodium metal, how many mol of magnesium metal can be precipitated with 12.6 mol of sodium metal? MgCl2(aq) + 2Na(s) --> 2NaCl(aq) + Mg(s)

2. A student correctly balanced the following chemical reaction, but forgot to include states of matter. What mass of solid precipitate can be expected to form if 23.08 g of silver nitrate is reacted with excess sodium carbonate? 2AgNO3 + Na2CO3 --> 2NaNO3 + Ag2CO3

3. When ammonia decomposes, it breaks down into nitrogen gas and hyrdogen gas. What mass of ammonia is needed to produce 50.00 g of hydrogen gas?​

Just a bit stuck, thanks a ton.