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Question 27

A student investigates the esterification reaction between propanoic acid, C2H5COOH(l)\text{C}_2\text{H}_5\text{COOH}(\text{l})C2​H5​COOH(l), and methanol, CH3OH(l)\text{CH}_3\text{OH}(\text{l})CH3​OH(l), in the presence of an acid catalyst to produce methyl propanoate and water:

C2H5COOH(l)+CH3OH(l)⇌C2H5COOCH3(l)+H2O(l) \text{C}_2\text{H}_5\text{COOH}(\text{l}) + \text{CH}_3\text{OH}(\text{l}) \rightleftharpoons \text{C}_2\text{H}_5\text{COOCH}_3(\text{l}) + \text{H}_2\text{O}(\text{l}) C2​H5​COOH(l)+CH3​OH(l)⇌C2​H5​COOCH3​(l)+H2​O(l)
a.

Explain why performing the kinetic study with a large excess of methanol allows the order of reaction with respect to propanoic acid to be determined directly.

[2]
b.

In a separate experiment to determine the equilibrium constant, KcK_cKc​, the student mixes 12.8 g12.8\text{ g}12.8 g of methanol (CH3OH\text{CH}_3\text{OH}CH3​OH) with 37.0 g37.0\text{ g}37.0 g of propanoic acid (C2H5COOH\text{C}_2\text{H}_5\text{COOH}C2​H5​COOH) and adds a small amount of acid catalyst.

When the mixture reaches equilibrium at constant temperature, 0.20 mol0.20\text{ mol}0.20 mol of C2H5COOH\text{C}_2\text{H}_5\text{COOH}C2​H5​COOH remains.

Calculate the value of KcK_cKc​ for this equilibrium.

[6]

Physical chemistry Questions

  1. A Level
  2. /Chemistry
  3. /Physical chemistry