Question

What is [H₃O⁺] in a solution of 0.075 M HNO₂ and 0.030 M NaNO₂? The pK, of HNO₂ is 4.35.

a. 1.8 x 10⁻⁵ M
b. 6.0 x 10⁻⁵ M
c. 1.1 x 10⁻⁴ M
d. 2.0 x 10⁻⁴ M

Answer 1

The [H₃O⁺] in the solution can be found using the equation [H₃O⁺] = √(Kₐ × [HNO₂]), where Kₐ is the acid dissociation constant. Given the values of [HNO₂] and [NO₂⁻], we can calculate [H₃O⁺] as 6.0 x 10⁻⁵ M.

Step-by-step explanation:

To find the [H₃O⁺] in the solution, we need to consider the dissociation of HNO₂. Nitrous acid (HNO₂) is a weak acid that partially ionizes in water, forming H₃O⁺ and NO₂⁻. The equilibrium expression for this dissociation is as follows: HNO₂ ⇌ H₃O⁺ + NO₂⁻.

Given that the [HNO₂] = 0.075 M and the [NO₂⁻] = 0.030 M, we can assume that x is the concentration of H₃O⁺ formed.

Using the equation [H₃O⁺] = √(Kₐ × [HNO₂]), where Kₐ is the acid dissociation constant, we can calculate the value of [H₃O⁺]. In this case, since pKₐ is given as 4.35, we can use Kₐ = 10^(-pKₐ).

Substituting the values into the equation, we get [H₃O⁺] = √((10^(-4.35)) × 0.075) = 6.0 x 10⁻⁵ M.