Question

In the reaction Mg (s) + 2HCl (aq) H2 (g) + MgCl2 (aq), how many moles of hydrogen gas will be produced from 75.0 milliliters of a 1.0 M HCl in an excess of Mg

Answer 1

Number of moles=Concentration(mole/L)*Volume(L)
There are 1,000 milliliters in a liter
1000 mL = 1 L
75.0 ml= x L
Cross multiplication to find x L
x=0.075 L
Number of moles=0.075*1=0.075 moles
2 moles of HCl react with 1 mole of Mg to produce 1 mole of H2 and MgCl2 according to the balanced chemical equation.
1:2:1:1
Mg:H2
2:1
0.075: y moles of H2
0.075*1/2=0.0375