Explanation:
CH2)3(g)CH3CH=CH2(g) [(CH2)3], M time, min
0.128 0
6.40×10-2 14.4
3.20×10-2 28.8
1.60×10-2 43.2
(1) What is the half-life for the reaction starting at t=0 min? min
Half life is the amount of time required for a substance to decay by half of it's initial concentration.
Starting form 0, the initial concentration = 0.128
After 14.4 mins, the final concentration is now exactly half of the initial concentration. This means 14.4 min is the half life starting from t=0min
What is the half-life for the reaction starting at t=14.4 min?
Starting form 14.4min, the initial concentration = 6.40×10-2
After 14.4 mins (28.8 - 14.4), the final concentration is now exactly half of the initial concentration. This means 14.4 min is the half life starting from t=14.4min
Does the half-life increase, decrease or remain constant as the reaction proceeds?
The half life is a constant factor, hence it remains constant as the reaction proceeds.
(2) Is the reaction zero, first, or second order?
Because the half life is independent of the concentration, it is a first order reaction.
In a zero order reaction, the half life Decreases as the reaction progresses; as concentration decreases.
In a first order reaction, the half life Increases with decreasing concentration.
(3) Based on these data, what is the rate constant for the reaction? min-1
The realtionship between the half life and rate onstant is;
k = 0.693 / half life
k = 0.693 / 14.4
k = 0.048125 min-1
