Question

`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?

Answer 1

1.85 g of hydrogen will form.

Explanation:

1. Write the balanced equation.

`"Zn" + "2HCl" → "ZnCl"_2 + "H"_2`

2. Calculate the moles of `"Zn"`.

`"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 `"H"_2`.

`"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 `"H"_2`.

`"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`