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#rate constant

118 public questions tagged with this topic.

CHEMISTRY

A first-order reaction is 25% complete in 15 minutes. What is the rate constant in min^{-1 ?

Given: A first-order reaction is 25% complete in 15 minutes. What is the rate constant in min^{-1 ? Formula: 25% complete, 75% remains: frac[R]_0[R] = 100/75 = 1.333. Substitution & Calculation: k = 2.303/t log frac[R]_0[R] = 2.303/15 log 1.333 = 0.0192 min^{-1 . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

Ref: NCERT Chemistry Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII), Chapter: Chemical Kinetics (Latest NCERT 2026-27), Topic: Arrhenius equation, k = A e^(-E_a/RT), activation energy and rate constant

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CHEMISTRY

A reaction has k = 1.0 × 10⁻³ s^{-1 at 27°C and E_a = 52 kJ mol^{-1 . What is the temperature (in °C) when k = 3.0

Given: A reaction has k = 1.0 × 10⁻³ s^{-1 at 27°C and E_a = 52 kJ mol^{-1 . What is the temperature (in °C) when k = 3.0 × 10⁻³ s^{-1 ? (R = 8.314 J/mol · K) These values define the system as per NCERT data. Formula: log frac3.0 × 10⁻³¹.0 × 10⁻³= 52000/2.303 × 8.314 ( T_2 - 300/300 T_2 ). This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 0.477 = 2717.5 ( T_2 - 300/300 T_2 ), T_2 approx 316 K = 43 °C . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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