Calculate how much hydrogen is formed when 28 g of lithium is dissolved in water.

Let’s write down the solution sequentially:
According to the condition of the problem, we compose the reaction equation
2Li + 2H2O = 2LiOH + H2 – redox reaction, hydrogen gas is released;
Let’s make calculations using the formulas:
M (Li) = 6.9 g / mol;
M (H2) = 2 g / mol;
Determine the amount of mol of lithium, if the mass is known:
Y (Li) = m / M = 28 / 6.9 = 4 mol;
Let’s make the proportion:
4 mol (Li) – X mol (H2);
-2 mol -1 mol hence, X mol (H2) = 4 * 1/2 = 2 mol;
We find the volume of hydrogen according to Avogadro’s law:
V (H2) = 2 * 22.4 = 44.8 liters.
Answer: in this reaction, 44.8 liters of hydrogen were released.