How do I do this stochiometry, what are the answers?

Question

Must show balanced equations, and the cancelations.

Problem #1:

Aluminum oxide is formed from the reaction of metallic aluminum with oxygen gas. How many moles of Aluminum are needed to form 3.4 moles of Aluminum oxide?

Problem #2:

Determine the number of grams of NH3 produced by the reaction of 3.5g of hydrogen gas with sufficient nitrogen gas.

Thank you in advance!

Answer 1

4Al +3 O2 >>2 Al2O3

the ratio between Al and Al2O3 is 4 : 2

Moles Al needed = 3.4 x 4 / 2 = 6.8

N2 + 3 H2 >> 2 NH3

moles H2 = 3.5 / 2 g/mol = 1.75

the ratio between H2 and NH3 is 3 : 2

Moles NH3 = 1.75 x 2 / 3 =1.17

Mass NH3 = 1.17 mol x 17 g/mol =19.9 g

Answer 2

Your balance equations will exhibit the correct proportions of oxygen and nitrogen. Stoichiometry implies the correct proportions, not too little or too much.