5. The effect of temperature on rate constants

Question 1

temperature increase=

Answer 1

rate increase

more successful collisions between atoms

Question 2

activation energy increase=

Answer 2

rate increase

overcome activation energy sooner

Question 3

purpose of arrhenius equation

Answer 3

links rate constant (k) with temperature
rate =K [A]x [B]y
if rate is increasing from temp and concentration stays same k must change

Question 4

arrhenius equation
K= Ae (to the power of) - Ea/ RT
what is stands for and units

Answer 4

K=rate constant 
A= pre-exponential factor. same units as K
e= inverse natural log
Ea= activation energy Jmol-1
R= gas constant 8.31 Jk-1mol-1
T = temperature in kelvin (273+/-)

Question 5

arrhenius equation

how does k change with high Ea

Answer 5

fraction gets bigger with large Ea
power more negative. 10-1 = 0.1 10-4= 0.0001
k lower
high Ea = low value for K

Question 6

arrhenius equation

how does k change with low Ea

Answer 6

fraction gets smaller with small Ea
power less negative. 10-4 = 0.0001 10-1 = 0.1
k higher
low Ea = higher value for K

Question 7

arrhenius equation

how does k change with high T

Answer 7

fraction smaller
power less negative
high temp= large k

Question 8

arrhenius equation

how does k change with low T

Answer 8

fraction bigger
power more negative
low temp = lower K

Question 9

things to remember in arrhenius calculations

Answer 9

units of k= units of A
Ea in Arrhenius= Jmol-1
Temp in K
LnA=x A= e to the power of x

Question 10

stuff about arhenius plots

Answer 10

based on lnk = -Ea + ln A
lnk= -Ea/R . 1/T        y = m x + c 
plot against 1/t gives straight line graph 
gradient -Ea/R
y intercept = ln A