need answers to problems.The balanced equation.and Your work showing cancellations.?

Question

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?
Hint: This is a simple ratio problem. Just use the molar ratio from the balanced equation. This was covered in 5.09. Mass is not involved.

Problem #2:
Determine the number of grams of NH3 produced by the reaction of 3.5g of hydrogen gas with sufficient nitrogen gas. (Check for diatomic elements). Use the flowchart below for help.

Given quantity in grams--> change to moles----> multiply by ratio from balanced equation -----> convert wanted quantity from moles to grams.

Answer 1

#1
4Al + 3O2 ===> 2Al2O3

3.4molAl2O3 x 4molAl/2molAl2O3 = 6.8 moles Al2O3

#2
N2 + 3H2 ===> 2NH3
Atomic weights: N=14 N2=28 H=1 NH3=17

3.5gN2 x 1molN2/28gN2 x 2molNH3/1molN2 x 17gNH3/1molNH3 = 4.25g NH3 (actually 4.2g to two significant figures)

Answer 2

4Al + 3O2 --> 2Al2O3
Twice as many moles of Al (4) required to produce moles of Al2O3 (2)
2 x 3.4 = 6.8 moles of Al required.

3H2 + N2 --> 2NH3
3.5g H2 = 3.5g / 2g per mole = 1.75 moles of H2
you get 2 moles of NH3 from 3 moles of H2
1.75 moles of H2 x (2/3) = 1.167 moles of NH3
1.167 moles of NH3 x 17 grams per mole = 19.8 g NH3