Zinc weighing 45.5 g was heated with 28 g of NaOH. The volume of released hydrogen is …

Let’s write down the solution step by step:
1. Let’s compose the reaction equation:
Zn + 2NaOH = Na2ZnO2 + H2 – redox reaction, hydrogen gas is released;
2. Calculations by formulas:
M (Zn) = 65.3 g / mol;
M (NaOH) = 39.9 g / mol;
Y (Zn) = m / M = 45.5 / 65.3 = 0.69 mol;
Y (NaOH) = m / M = 28 / 39.9 = 0.7 mol;
3. Let us compose the proportion according to the reaction equation data, the calculation is carried out for the substance in deficiency, that is, for zinc:
0.69 mol (Zn) – X mol (H2);
-1 mol              -1 mol hence, X mol (H2) = 0.69 * 1/1 = 0.69 mol;
4. Let’s calculate the volume of hydrogen, applying Avogadro’s law:
V (H2) = 0.69 * 22.4 = 15.45 liters.
Answer: during the reaction, hydrogen is released in a volume of 15.45 liters.