What volume of hydrogen will be released if 1.15 ml of absolute alcohol (p = 0.8 g / ml) reacted with 2 mol of sodium.

Given:
V solution (C2H5OH) = 1.15 ml
ρ solution (С2Н5ОН) = 0.8 g / ml
n (Na) = 2 mol

To find:
V (H2) -?

Decision:

Solving the problem, it is necessary to fulfill the following main points:

write the equation of the chemical reaction, which is indicated in the condition of the problem, and be sure to correctly place the coefficients in front of the substances;
calculate the molar masses of the substances used in the problem, guided by the table of D. I. Mendeleev;
check the units of measurement provided in the condition for compliance with the SI system; if there is a discrepancy, translate them;
know the definition of the term “absolute alcohol”, “amount of substance”;
carry out calculations using the necessary formulas.
Calculations based on known data
1) Write the reaction equation:
2C2H5OH + 2Na => 2C2H5OHA + H2 ↑;

2) In the problem, we need the molar mass of С2Н5ОН, since Na is already given in the form of an amount of substance, and Н2 is a gas (in the formula for finding the volume of gas, the molar mass is not used). Using the periodic system of D.I.Mendeleev, make a calculation that will be numerically equal to the molecular weight:
Mr (C2H5OH) = Ar (C) * 2 + Ar (H) * 6 + Ar (O) = 12 * 2 + 1 * 6 + 16 = 46 g / mol;

3) Calculate the mass of the C2H5OH solution:
m solution (С2Н5ОН) = ρ solution (С2Н5ОН) * V solution (С2Н5ОН) = 0.8 * 1.15 = 0.92 g;

4) Since according to the condition absolute alcohol is given (practically free of water), the water content in it can be neglected. So we can find the mass of С2Н5ОН:
m (C2H5OH) = m solution (C2H5OH) = 0.92 g;

5) Determine the amount of substance С2Н5ОН:
n (C2H5OH) = m (C2H5OH) / Mr (C2H5OH) = 0.92 / 46 = 0.02 mol;

6) When comparing the amount of the substance C2H5OH and Na, it turns out that the amount of the substance C2H5OH is in short supply, so the calculations will be carried out for it;

Finding the volume of hydrogen
7) Taking into account the reaction equation, the amount of substance H2 should be calculated:
n (H2) = n (C2H5OH) / 2 = 0.02 / 2 = 0.01 mol;

8) Find the volume of the released H2 gas:
V (H2) = n (H2) * Vm = 0.01 * 22.4 = 0.224 l.

Answer: The volume of released H2 is 0.224 liters.