A monobasic saturated carboxylic acid weighing 60 g completely reacts with 12 g of magnesium.

| February 11, 2021 | education

A monobasic saturated carboxylic acid weighing 60 g completely reacts with 12 g of magnesium. The molecular weight of the acid is equal to the molecular weight of propanol. Determine the acid formula, name it.

Let RCOOH be a saturated monobasic carboxylic acid, where R is an unknown alkyl radical.

Let’s write the reaction equation:

2RCOOH + Mg = (RCOO) 2Mg + H2 ↑

Let’s find the amount of magnesium substance:

v (Mg) = m (Mg) / M (Mg) = 12/24 = 0.5 (mol).

According to the reaction equation, 2 mol of RCOOH reacts with 1 mol of Mg, therefore:

v (RCOOH) = v (Mg) * 2 = 0.5 * 2 = 1 (mol).

Find the molar mass of RCOOH:

M (RCOOH) = m (RCOOH) / v (RCOOH) = 60/1 = 60 (g / mol), which, as stated in the condition, coincides with the molar mass of propanol (M (C3H7OH) = 60 (g / mol) ).

Let’s find the molar mass R:

M (R) = M (RCOOH) – M (COOH) = 60 – 45 = 15 (g / mol), which corresponds to the methyl radical (-CH3), whence the formula of the saturated monobasic carboxylic acid: CH3COOH (acetic acid).



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