Answer:
Theoretical yield of hydrogen is 1.11 g
Explanation:
Balanced equation, 
As Mg remain present in excess therefore HCl is the limiting reagent.
According to balanced equation, 2 moles of HCl produce 1 mol of
.
Molar mass of HCl = 36.46 g/mol
So, 40.0 g of HCl =
of HCl = 1.10 moles of HCl
Hence, theoretically, number of moles of
are produced from 1.10 moles of HCl = 
Molar mass of
= 2.016 g/mol
So, theoretical yield of
= 
Answer:
Any of the answers given will work
Explanation:
I literally just did it.
The law of conservation of mass states that mass is neither created nor destroyed. Since we have 2 g/mol of A and 3 g/mol of B then AB should be equal to the sum of their molar mass that is
2 g/mol + 3 g/mol = 5 g/mol AB
for the case of A2B3
A2 = 2 * 2 = 4 g/mol
B3 = 3 * 3 = 9 g/mol
therefore A2B3 = 13 g/mol