# Zn(s) + 2HCl(aq) -> H_2 (g) + ZnCl_2(aq) + heat energy. If 30.0 g of Zn react, how many grams of H_2 will form?

Jul 2, 2016

1.85 g of hydrogen will form.

#### Explanation:

1. Write the balanced equation.

${\text{Zn" + "2HCl" → "ZnCl"_2 + "H}}_{2}$

2. Calculate the moles of $\text{Zn}$.

$\text{Moles of Zn" = 30.0 color(red)(cancel(color(black)("g Zn"))) × ("1 mol Zn")/(65.38 color(red)(cancel(color(black)("g Zn")))) = "0.4589 mol Zn}$

3. Calculate the moles of ${\text{H}}_{2}$.

${\text{Moles of H"_2 = 0.4589 color(red)(cancel(color(black)("mol Zn"))) × ("2 mol H"_2)/(1 color(red)(cancel(color(black)("mol Zn")))) = "0.9177 mol H}}_{2}$

4. Calculate the mass of ${\text{H}}_{2}$.

${\text{Mass of H"_2 = 0.9177 color(red)(cancel(color(black)("mol H"_2))) × ("2.016 g H"_2)/(1 color(red)(cancel(color(black)("mol H"_2)))) = "1.85 g H}}_{2}$