Problem 40 - Chemistry: An Atoms-Focused Approach

Question

Rank the conductivities of \(1 M\) aqueous solutions of each of the following solutes, starting with the most conductive: (a) acetic acid; (b) methanol; (c) sucrose (table sugar); (d) hydrochloric acid.

Step-by-Step Solution

Answer

Question: Rank the conductivities of 1 M aqueous solutions of the following solutes, starting with the most conductive: (a) acetic acid, (b) methanol, (c) sucrose, and (d) hydrochloric acid. Answer: (d) Hydrochloric acid > (a) Acetic acid > (b) Methanol, (c) Sucrose

Step 1: Identify the type of each solute and their dissociation in water

First, identify whether each solute is an electrolyte or a nonelectrolyte. Electrolytes dissociate into ions when it dissolves in water, whereas nonelectrolytes do not dissociate into ions. Acetic acid is a weak acid (weak electrolyte) and partially dissociates into ions; methanol is an alcohol (nonelectrolyte); sucrose is a sugar (nonelectrolyte); and hydrochloric acid is a strong acid (strong electrolyte) and completely dissociates into ions.

Step 2: Determine the number of ions produced by each solute in 1 M solution

(a) Acetic acid (\(CH_3COOH\)) dissociates partially in water and produces two ions: \(CH_3COOH \rightleftharpoons CH_3COO^- + H^+\) (b) Methanol (\(CH_3OH\)), being a nonelectrolyte, does not dissociate into ions in water. (c) Sucrose (\(C_{12}H_{22}O_{11}\)), being a nonelectrolyte, does not dissociate into ions in water. (d) Hydrochloric acid (\(HCl\)) dissociates completely in water and produces two ions: \(HCl \rightarrow Cl^- + H^+\)

Step 3: Rank the conductivities

Now that we know the number of ions produced by each solute, we can rank them based on their conductivity. Since conductivity is directly proportional to the number of ions present: 1. Hydrochloric acid - strong electrolyte, dissociates completely into ions, highest conductivity 2. Acetic acid - weak electrolyte, dissociates partially into ions, moderate conductivity 3. Methanol and sucrose - nonelectrolytes, do not dissociate into ions, lowest conductivity Thus, the final ranking is: (a) acetic acid; (b) methanol; (c) sucrose (table sugar); and (d) hydrochloric acid: (d) > (a) > (b), (c)