What will happen when the temperature of a chemical reaction rises by 10 °C?

rate constant is nearly doubled.

The correct answer is Option (2) → rate constant is nearly doubled.

According to the rule of thumb in chemical kinetics (van't Hoff rule), for most chemical reactions, the rate constant (k) approximately doubles (or increases 2–3 times) when the temperature is increased by 10 °C. This is because the rate constant follows the Arrhenius equation:

$k = A e^{-E_a / RT}$

where:

• $E_a$​: Activation energy
• R: Gas constant
• T: Absolute temperature

A 10 °C rise increases T, which decreases the exponential term's negative exponent (since $E_a / RT$ becomes smaller), leading to a significant increase in k.

• For typical reactions with $E_a$​ around 50–100 kJ/mol near room temperature, the factor is roughly 2–3 times (often approximated as "doubled").
• Exact multiplication depends on $E_a$​ and initial temperature, but "nearly doubled" is the standard approximation taught.

Why others are incorrect:

• Rate constant remains same: Incorrect; k is temperature-dependent.
• Rate constant decreases: Incorrect; higher temperature increases k.
• Rate constant increases by 10 times: Incorrect; too large (would require much higher $E_a$​ or larger temperature jump).