Question

CO₂, H₂CO₃, HCO₃ ⁻ and CO₃ ²⁻. Rank these in order of increasing attraction to water molecules.

Answer 1

Answer: The order of increasing attraction to water molecules is as follows:

1. CO₂

2. CO₃ ²⁻

3. H₂CO₃

4. HCO₃ ⁻

Explanation: Carbon dioxide (CO₂) is a nonpolar molecule and has no charge, so it has the least attraction to water molecules. Carbonate (CO₃ ²⁻) has a charge but is a large ion, so it has a weaker attraction to water molecules than the smaller ions. Carbonic acid (H₂CO₃) and bicarbonate (HCO₃ ⁻) are polar molecules with hydrogen bonds, so they have a stronger attraction to water molecules than CO₂ and CO₃ ²⁻.

Answer 2

The pH of an air-saturated water solution with a hydronium ion concentration from dissolved CO2 of 2.0 × 10^-6 M at 25 °C is approximately 5.7.

Step-by-step explanation:

The student is asking about the relative attractions of different carbon-containing species to water molecules and to calculate the pH of a solution containing dissolved carbon dioxide at a given temperature. To answer the pH part: given that air-saturated water has a hydronium ion concentration (H3O+) caused by the dissolved CO2 of 2.0 × 10-6 M, you can calculate pH using the equation pH = -log[H3O+].

Inserting the values:

pH = -log(2.0 × 10-6)
≈ 5.7

Therefore, the pH of the solution is approximately 5.7.