FC
Reactivity 2.2 Flashcards
Active Recall for Rate of Change
Flashcards: read all 10 questions and answers
- State two conditions for a successful collision.1. Particles must collide with energy greater than or equal to the activation energy (\(E_{\text{a}}\)). 2. Particles must collide with the correct orientation.
- What does the Maxwell-Boltzmann distribution show?The distribution of kinetic energies among particles at a given temperature. The area under the curve = total number of particles.
- How does increasing temperature affect the MB distribution?The curve shifts right and flattens (broader). The peak is lower. More particles have energy \(\ge E_{\text{a}}\), so rate increases.
- How does a catalyst increase rate?It provides an alternative reaction pathway with a lower activation energy. More particles exceed this lower \(E_{\text{a}}\), so the rate of successful collisions increases.
- Does a catalyst change ΔH?No. A catalyst only lowers \(E_{\text{a}}\). The enthalpy change (ΔH) of the reaction is the same with or without a catalyst.
- How do you find the rate from a concentration-time graph?Draw a tangent to the curve at the desired time. The gradient (slope) of the tangent = instantaneous rate.
- State the rate equation format (HL).Rate = k[A]^m[B]^n, where k = rate constant, m and n = orders found experimentally.
- How do you find the order using initial rates? (HL)Compare experiments where only one [reactant] changes. If doubling [A] has no effect: order 0. Doubles rate: order 1. Quadruples rate: order 2.
- State the Arrhenius equation (HL).\(k = A e^{-\frac{E_{\text{a}}}{RT}}\). In linear form: \(\ln k = \ln A - \left(\frac{E_{\text{a}}}{R}\right)\left(\frac{1}{T}\right)\). A plot of \(\ln k\) against \(1/T\) gives a straight line with gradient \(= -\frac{E_{\text{a}}}{R}\).
- Why does rate decrease over time in a reaction?As reactants are consumed, their concentration decreases. Fewer particles means fewer collisions per second, so the rate drops.