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Given pH = 3.50 Find: [H3O+] and [OH-] Is this acidic, basic or neutral?

User Yoel Nunez
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1 Answer

2 votes

Answer:

Step-by-step explanation:

Given parameters:

pH = 3.50

Unknown:

concentration of [H₃0⁺] = ?

concentration of [OH⁻] = ?

Solution:

In order to find the unknown, we use some simple expressions which best explains the pH scale and the equilibrium systems of aqueous solutions.

pH = -log₁₀[H₃O⁺]

[H₃O⁺] = inverse log₁₀ (-pH) =
10^(-pH) =
10^(-3.5)

[H₃O⁺] = 3.2 x 10⁻⁴moldm⁻³

For the [OH⁻]:

we use : pOH = -log₁₀ [OH⁻]

Recall: pOH + pH = 14

pOH = 14 - pH = 14 - 3.5 = 10.5

Now we plug the value of pOH into pOH = -log₁₀ [OH⁻]

[OH⁻] =
10^(-pOH)

[OH⁻] =
10^(-10.5) = 3.2 x 10⁻¹¹moldm⁻³

The solution is acidic as the concentration of H₃0⁺ is more than that of the OH⁻ ions.

User Kyle Barnes
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