For a neutral aqueous solution with pH = 7 at 25°C, what is the value of [H+][OH−]?

Introduction / Context:The ionic product of water, Kw, underpins acid–base calculations. At 25°C, neutral water has equal hydrogen and hydroxide ion concentrations, and their product is a small constant value central to pH and pOH relationships.

Given Data / Assumptions:

• Neutral solution at 25°C: pH = 7 implies [H+] = 10^-7 mol/L.
• In neutrality, [H+] = [OH−].

Concept / Approach:Kw = [H+][OH−] = 10^-14 at 25°C. Because both [H+] and [OH−] are 10^-7 mol/L, their product is 10^-14, which is far less than 1 in magnitude.

Step-by-Step Solution:At pH 7: [H+] = 10^-7 mol/L.Neutrality: [OH−] = 10^-7 mol/L.Product: [H+][OH−] = 10^-14, which is numerically < 1.

Verification / Alternative check:Also, pKw = 14 at 25°C → Kw = 10^-14 confirms the result.

Why Other Options Are Wrong:0 is impossible in water; 1 is off by 14 orders of magnitude; > 1 is physically inconsistent at 25°C; “exactly 10^-7” confuses concentration with the product.

Common Pitfalls:Confusing pH with [H+]; forgetting temperature dependence of Kw (though the question specifies 25°C).

Final Answer:< 1