18.5 - Rate constants and temperature Flashcards Preview

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Flashcards in 18.5 - Rate constants and temperature Deck (15):
1

What is the effect on the rate constant if the temperature increases?

The rate constant also increases

2

Why does increasing temperature increase the rate constant?

Boltzmann distribution shifts right, increasing the proportion of particles that exceed the activation energy

Particles move faster and therefore collide more frequently (higher chance of correct orientation)

3

What is the Arrhenius equation?

k = A e -Ea/RT

4

What is k in the Arrhenius equation?

Rate constant

5

What is A in the Arrhenius equation?

Pre-exponential factor

6

What is e -Ea/RT in the Arrhenius equation?

Exponential factor

7

What is Ea?

Activation energy

8

What is R in the Arrhenius equation?

Gas constant = 8.314 J mol-1 K-1

9

What are the units for R?

J mol-1 K-1

10

What are the units for T in the Arrhenius equation?

K

11

What does the exponential factor represent?

The proportion of molecules that exceed Ea and have sufficient energy for a reaction to take place

12

What does the pre-exponential factor represent?

The frequency of collisions with the correct orientation

13

What is the logarithmic form of the Arrhenius equation?

ln k = -Ea/RT + ln A

14

What would be the X and Y axes on a graph that represents the Arrhenius equation? What would the gradient and the y-intercept represent?

X-axis = 1/T
Y-axis = ln k
Gradient = -Ea/R
y-intercept = ln A

15

What are the units for Ea?

kJ mol-1