Chapter 18- Rates of reactions

Question 1

Rate of reaction definition

Answer 1

change in concentration of a reactant or product per unit time/ how frequently successful collisions take place

Question 2

Overall order definition

Answer 2

Sum of the individual orders

Question 3

Rate constant definition (K)

Answer 3

constant that links the rate of reaction with the concentration of the reactants raised to the powers of their orders in the rate equation

Question 4

Rate equation

Answer 4

A+B ->C is given by rate= k[A]^m [B]^n

Question 5

Orders of reaction theory

Answer 5

concept that if there is more than one reactant in a reaction, one reactant can affect the rate of reaction more/less than the other

Question 6

Zero order reactions

Answer 6

• if the order is 0 with the respect to reactant A, then rate is proportional to [A]^0
• the rate is unaffected by changing the concentration of A
  (any number to the power of 0 is equal to 1)

Question 7

First order reactions

Answer 7

• if the order is 1 with respect to a reactant B, then the rate is proportional to [B]^1
• the rate is directly proportional to the concentration
• if [B] increases by 2x, the rate also increases by 2x

Question 8

Second order reactions

Answer 8

• if the order is 2 with respect to a reactant C, then the rate is proportional to [C]^2
• the change in rate will be equal to the change in (concentration)^2
• if [C] increases by 2x, the rate increases by 4x

Question 9

Units of k

Answer 9

mol dm^-3 s^-1

Question 10

Zero order reactions units

Answer 10

• rate= k[A]^0 =k
• k= rate/1
• units= mol dm^-3 s^-1

Question 11

First order reactions units

Answer 11

• rate= k[A]
• k= rate/ [A]
• units= s^-1

Question 12

Second order reaction units

Answer 12

• rate= k[A]^2
• k= rate/ [A]^2
• units= mol^-1 dm^-3 s^-1

Question 13

Third order reaction units

Answer 13

• rate= k[A]^2 [B]
• k= rate/ [A]^2 [B]
• units= mol^-2 dm^6 s^-1

Question 14

How do you find the rate of a reaction using a graph

Answer 14

• Plot concentration against time (after experiment where the concentration is measured in intervals)
• The gradient of the line represents the rate
• If the data produces a curve, a tangent is drawn against the curve

Question 15

Zero order concentration-time graphs

Answer 15

• Produces a straight line graph
• Concentration decreases at a constant rate
• The half-life decreases with time