Determine the molecular formula of the alcohol, from 7.4 g of which sodium displaces 1.12 liters of hydrogen.
July 27, 2021
1. Let’s compose the reaction equation:
2R – OH + 2Na = H2 + RO – Na – substitution reaction, hydrogen gas is released;
2. Determine the number of moles of H2 according to Avogadro’s law:
1 mol (H2) – 22.4 L;
X mol – 1.12 liters from here;
X mol (H2) = 1.12 * 1 / 22.4 = 0.05 mol;
3. We make the proportion according to the reaction equation:
X mol (R-OH) – 0.05 mol (H2);
-2 mol -1 mol from here,
X mol (R-OH) = 0.05 * 2/1 = 0.1 mol;
4. Let’s calculate the molar mass of alcohol according to the formula: Y (ROH) = m (ROH) / M (ROH);
M (ROH) = 7.4 / 0.1 = 74 g / mol.
5. Let’s define the formula of alcohol: M (C4H9 – OH) = 12 * 4 + 10 + 16 = 74 g / mol.
Answer: butanol is involved in the substitution reaction, M (C4H9 – OH) = 74 g / mol.
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