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What is the pH value of a neutral solution at 25°C?
0
7
14
1
7
At 25°C, a neutral solution has a pH value of 7. The provided answer key indicating 1 is scientifically incorrect, as 1 represents a highly acidic solution.
At 25°C, a neutral solution has a pH value of 7. The provided answer key indicating 1 is scientifically incorrect, as 1 represents a highly acidic solution.
Think of the pH scale like a balance beam; 7 is the perfectly balanced fulcrum, while numbers below 7 are tipping toward the 'acid' side and above 7 toward the 'base' side.
Neutral is Natural seven (S-e-v-e-n is neutral).
pH=−log10[H3O+] — Definition of pH
Kw=[H3O+][OH−]=10−14 — Ionic product of water at 25°C
The pH scale is defined by the negative logarithm of the hydronium ion concentration, given as pH=−log[H3O+]. At 25°C, the ionic product of water (Kw) is 1.0×10−14. In a neutral solution, the concentration of [H3O+] equals [OH−], resulting in [H3O+]=1.0×10−7M, which yields pH=7.
pH 7 is neutral at 25°C.
pH < 7 is acidic (high [H3O+] concentration).
pH > 7 is basic (high [OH−] concentration).
Provides a logarithmic scale to express wide ranges of ion concentrations conveniently.
Temperature dependency: The neutral pH point shifts as temperature changes due to the variation in Kw.
Measuring blood plasma pH (approx 7.4).
Soil quality testing in agriculture.
Pure distilled water is the standard for a neutral solution.
Option D (1) is incorrect because it describes a strong acid, not a neutral solution.
B is correct — A neutral solution has a pH of 7 at 25°C because the concentration of hydronium ions is exactly 10−7mol/L.
Always check the temperature condition in pH questions, as Kw changes with temperature, which can shift the neutral point.
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