Calculate the concentration of OH⁻ in a 0.01 M HCl solution at 25 °C, and classify the solution as acidic or basic.

• A. 1.0 x 10⁻¹² M, acidic
• B. 1.0 x 10⁻⁷ M, neutral
• C. 1.0 x 10⁻¹⁰ M, basic
• D. 1.0 x 10⁻² M, basic

Answer: (A)

Verified step by step guidance

1. Start by understanding that HCl is a strong acid, which means it dissociates completely in water. Therefore, the concentration of H⁺ ions in the solution is equal to the initial concentration of HCl, which is 0.01 M.
2. Use the ion product of water (Kw) at 25 °C, which is 1.0 x 10⁻¹⁴. The relationship between the concentrations of H⁺ and OH⁻ ions in water is given by the equation: $Kw=\; [H+][\mathrm{OH}-]$.
3. Substitute the known values into the equation: $1.0\; x\; 10⁻¹⁴\; =\; [0.01][\mathrm{OH}-]$. Solve for the concentration of OH⁻ ions.
4. Calculate the concentration of OH⁻ ions by rearranging the equation: $[\mathrm{OH}-]\; =\frac{\mathrm{1.0\; x\; 10⁻¹⁴}}{0.01}$.
5. Determine the nature of the solution. Since the concentration of H⁺ ions is greater than that of OH⁻ ions, the solution is classified as acidic.