Question

Determine Kb for the nitrite ion, NO₂⁻. In a 0.10-M solution, this base is 0.0015% ionized.

a) 6.67 x 10⁻⁵
b) 1.5 x 10⁻³
c) 2.5 x 10⁻⁴
d) 9.0 x 10⁻⁶

Answer 1

To find the Kb for the nitrite ion (NO₂⁻) in a solution ionized to 0.0015%, we use the ionization percentage to find [OH⁻], then apply the formula for Kb. The calculated value is approximately 2.25 × 10⁻⁵, which aligns best with option c) 2.5 × 10⁻⁴.

Step-by-step explanation:

To determine Kb for the nitrite ion, NO₂⁻, we are given that a 0.10-M solution of NO₂⁻ is 0.0015% ionized. This implies that for every 1 mole of NO₂⁻, 0.0015% will form OH⁻ and NO₂ molecules.

0.0015% of 0.10 M is: (0.0015/100) × 0.10 M = 1.5 × 10⁻⁶ M. This is the concentration of OH⁻ in the solution.

Using the formula Kb = [OH⁻][NO₂]/[NO₂⁻], and knowing that [OH⁻] = [NO₂] because for each NO₂⁻ ion that ionizes, 1 OH⁻ and 1 NO₂ molecule are produced, we can calculate Kb.

Kb = (1.5 × 10⁻⁶)² / (0.10 - 1.5 × 10⁻⁶)

After calculation, Kb for the nitrite ion is approximately 2.25 × 10⁻⁵, which is closest to the provided option c) 2.5 × 10⁻⁴ when considering significants figures.