Question

Calculate the concentration of H3O in a solution that contains 5.5 × 10-5 M OH at 25°C. Identify the solution as acidic, basic or neutral. Group of answer choices 5.5 × 10-10 M, neutral 9.2 × 10-1 M, basic 9.2 × 10-1 M, acidic 1.8 × 10-10 M, basic

Answer 1

Answer:

The correct option is option (D).

Therefore the concentration of $H_3O$ is 1.8×10⁻¹⁰ M and it is basic in nature.

Explanation:

List of pH:

1. If pH of a solution is 7, then solution is neutral.
2. If pH of a solution is grater than 7, then solution is basic.
3. If pH of a solution is less than 7, then solution is acidic.

pH of a solution is = - log₁₀[H₃O⁺]

We know that,

[H₃O⁺][OH⁻] = $K_w$ = $10^{-14}$  (at 25°C)

Taking log both sides

log ([H₃O⁺][OH⁻]) =log $K_w$ =log $10^{-14}$

⇒log[H₃O⁺]+log[OH⁻] = log$K_w$ = -14 log 10

[since log(mn)= log m + log n, $log( a^b)=b\ log (a)$ ]

⇒ - log[H₃O⁺] - log[OH⁻] = - (-14)  [ log 10 =1]

⇒pH+pOH =14.

Given that,

The concentration of OH⁻ is 5.5 × 10⁻⁵ M

[H₃O⁺][OH⁻] = $K_w$ = $10^{-14}$

⇒[H₃O⁺] 5.5 × 10⁻⁵ M=10⁻¹⁴

$\Rightarrow [H_3O^+]=\frac{10^{-14}}{5.5\times 10^{-5}}$

⇒[H₃O⁺] = 1.8×10⁻¹⁰ M

Now check the pH of the solution.

[H₃O⁺] = 1.8×10⁻¹⁰

Taking log both sides

log [H₃O⁺] =log( 1.8×10⁻¹⁰)

⇒ -log [H₃O⁺] = - log( 1.8×10⁻¹⁰)

⇒ pH = - log( 1.8×10⁻¹⁰)

⇒ pH =9.7.

So the nature of solution is basic.

Therefore the concentration of $H_3O$ is 1.8×10⁻¹⁰ M and it is basic in nature.