RATES

Question 1

what is the rate of reaction

Answer 1

the change in concetration of a reactant or product per unit of time

Question 2

what are the units of rate

Answer 2

mol dm3 s-1

Question 3

define the term initial rate of reaction

Answer 3

the chage in concetration of a reactant or product per unit of time at the start of the reaction when t=o

Question 4

how is the rate of reaction measured from a concetration time graph

Answer 4

a tangent is drawn to the cureve at the required time and the gradiant of the tangent is measured (change in Y divided by chage in x)

Question 5

define the term order of reaction

Answer 5

the order with respect to a reactant is the pwer to which the concetration of the reactant is raised in the rate equation.

Question 6

how can we find out how the concetration of a reactant affects th reaction rate

Answer 6

by carrying our experiaments we can find out the effect or the order with respect to a reactant

Question 7

the rate equation for a reaction is

Question 8

what does it mean id the orders is 0,1,2 with respect to a reactant

Answer 8

• if its 0 order:the rate is unaffected by changing the concetration of the reactant.
• if its 1st order: if the reactant doubles the rate of reaction will also double(increase by 2)
• if its 2 order:when the reactant doubles the rate of reaction increases by a factor of 4.

Question 9

what is the rate constant

Answer 9

the constant that links the rate of reaction with the concetrations of the reactant raised to the powers if their order in the rate equation

Question 10

define the term half life

Answer 10

half life of a reactant is the time taken for the concetration of the reactant to reduce by half.

Question 11

why can a first order reaction be easily identified from the concetration-time graph.

Answer 11

• a first order reaction has a constant half life
• the half life is the same no matter what the concetration is

Question 12

draw concetration -time graphs of 0,1,2 orders

Question 13

draw rate concetration graph of orders 0,1,2

Question 14

what is the effect of temperature on the rate constant

Answer 14

the higher the temperature the larger the value of K

Question 15

define the term reaction mechanism

Answer 15

series of steps that together make up the overall reaction.

Question 16

define the term rate determining step

Answer 16

slowest step in the reaction mechanism of multi step reaction

Question 17

can we detemine the reaction mechanism from the overall reaction

Answer 17

no,because experiaments have to be carried out to detemine this.

Question 18

what does it mean if a reactant appears in the rate equation

Answer 18

it means that the reactant is inolved in the rate determinig step.

Question 19

what is an intemediate

Answer 19

• species formed in one step of the multi step reaction
• that is used up in the subsequent reaction
• and is not seen as either a reactant or product of the overall equation.