How many grams of water are formed when 10 liters of hydrogen are burned?

Given:
V (H2) = 10 l

To find:
m (H2O) -?

Decision:
1) Write the equation of a chemical reaction:
O2 + 2H2 => 2H2O;
2) Using the periodic system of D.I.Mendeleev, calculate the molar masses of H2 and H2O, which will be numerically equal to the molecular weights:
Mr (H2) = Ar (H) * 2 = 1 * 2 = 2 g / mol;
Mr (H2O) = Ar (H) * 2 + Ar (O) = 1 * 2 + 16 = 18 g / mol;
3) Calculate the amount of substance H2:
n (H2) = V (H2) / Vm = 10 / 22.4 = 0.45 mol;
4) Calculate the amount of substance H2O (taking into account the coefficients in the reaction equation):
n (H2O) = n (H2) = 0.45 mol;
5) Calculate the mass of H2O:
m (H2O) = n (H2O) * Mr (H2O) = 0.45 * 18 = 8.1 g.

Answer: The mass of H2O is 8.1 g.