Calculate the mass of hydrogen, which is formed if 0.8 g of calcium is placed in water.

Let’s implement the solution:

In accordance with the condition of the problem, we write:
m = 0.8 g X g -?

Ca + 2H2O = Ca (OH) 2 + H2 – OBP, hydrogen was obtained;

We make calculations:
M (Ca) = 40 g / mol;

M (H2) = 2 g / mol.

Determine the amount of the original substance:
Y (Ca) = m / M = 0.8 / 40 = 0.02 mol.

Y (H2) = 0.02 mol since the amount of substances is equal to 1 mol.

Find the mass of the product:
m (H2) = Y * M = 0.02 * 2 = 0.04 g

Answer: the mass of hydrogen is 0.04 g