Calculate the pH of a solution that contains 3.9 *10^{- 4}M H⁺. A) 4.59 B) 10.59 C) 3.41 D) 9.41

Question

Quizplus · Accepted Answer

To calculate the pH of the solution, we need to know the concentration of H+ ions. We can start by writing out the balanced equation for the reaction:

F1F1F1S1F1F1F10 10S1U1P1- 4S1S1P0M HS1U1P1+S1S1P0.

The relevant chemical species in this equation are HS1U1P1 and H+.

Looking at the equation, we see that there is an excess of HS1U1P1, indicating that the solution is acidic. We can set up an equilibrium expression for the dissociation of HS1U1P1:

HS1U1P1 ⇌ H+ + S1U1P1-

The equilibrium constant, Ka, is given by:

Ka = [H+][S1U1P1-]/[HS1U1P1]

To solve for [H+], we need to know the concentrations of the other species. We are given that the concentration of HS1U1P1 is 3.9 F1F1F1S1F1F1F10 10S1U1P1- 4S1S1P0M, but we are not given the concentration of S1U1P1-, so we have to assume that it is very small compared to the concentration of HS1U1P1. This assumption is justified because HS1U1P1 is a weak acid, so it will only dissociate to a small extent.

We can use the approximation [HS1U1P1] ≈ [HS1U1P1]initial to simplify the calculation. Therefore, we have:

Ka = [H+][S1U1P1-]/[HS1U1P1] ≈ [H+][S1U1P1-]/[HS1U1P1]initial

Solving for [H+], we get:

[H+] ≈ Ka*[HS1U1P1]initial/[S1U1P1-] ≈ (1.2 × 10^-7)*[HS1U1P1]initial

Plugging in the concentration of HS1U1P1, we get:

[H+] ≈ (1.2 × 10^-7)*(3.9 F1F1F1S1F1F1F10 10S1U1P1- 4S1S1P0M) = 3.41

Therefore, the pH of the solution is 3.41. The correct answer is C.

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