Orders and Rate Equations

Question 1

Reaction rate usually determines by

Answer 1

Concentration change with time

Question 2

0 order with respect to A

Answer 2

Rate is unaffected by changes in A’s concentration

Rate = [A]0

Question 3

Rate units

Answer 3

Mol dm-3 s-1

Question 4

First order re: B

Answer 4

Rate is doubled by doubling B’s concentration

Question 5

Second order re: C

Answer 5

Rate is quadrupled by doubling C’s concentration

Question 6

Rate equation

Answer 6

Rate=k[A]0[B]1[C]2

k= constant of reaction

Question 7

Large k vs small k

Answer 7

Large=fast reaction rate

Small=slow reaction rate

Question 8

Graphs measure?

Answer 8

Half-life of a reactant

Question 9

First-order concentration/time graph

Answer 9

Constant half-life therefore halves in equal time intervals

Even slope

Question 10

Zero-order concentration/time graph

Answer 10

Falls at steady rate
Half-life decreases with tome
Straight negative diagonal

Question 11

Second order concentration/time graph

Answer 11

Half life gets progressively longer, therefore increases with time
Line gets more curved

Question 12

Zero order rate/concentration graph

Answer 12

Straight horizontal line

Question 13

First order rate/concentration graph

Answer 13

Straight positive diagonal line

Question 14

Second order rate/concentration graph

Answer 14

Positive sloped diagonal line
Or
Graph plotting rate/[A]2 to get straight horizontal line

Question 15

Third order reaction equation

Answer 15

k[X(aq)]2 Y(aq)]

Question 16

Rate constant equation

Answer 16

k= rate/[X]2[Y]

Question 17

Zero order unit

Answer 17

Rate=k[A]0=k

Unit = mol dm-3 s-1

Question 18

First order

Answer 18

Rate=k[A]

unit = s-1

Question 19

Second order

Answer 19

Rate=k[A]2

Unit= dm3 mol-1 s-1

Question 20

Third order

Answer 20

Rate=k[A]2 [B]

unit=dm6 mol-2 s-1

Question 21

Rate determining step

Answer 21

Slowest step, main control of reaction rate

Rate equation therefore only includes reacting species of this step

Question 22

Kc

Answer 22

Equilibrium constant

Question 23

Equilibrium law

Answer 23

aA+bB = cC+dD
Letters are equil concentrations
Each one has its concen. raised to the power of its balancing number in the equation

Question 24

Equilib concentration equaton

Answer 24

Products multiplied together/reactants multiplied together

Question 25

Kc units

Answer 25

Do Kc equation but with their units instead

Question 26

Kc properties

Answer 26

Kc=1: equil halfway between reactants and products
Kc=100: equil in favour of products
Kc=1x10-2: equil in favour of reactants
Kc is ONLY changed by altering temperature
Kc shows how far a reaction proceeds, NOT how fast

Question 27

Kc temperature link

Answer 27

Exothermic reaction=Kc decrease with temperature increase

Endothermic reaction=Kc increase with temperature increase

Question 28

I.C.E. table?

Answer 28

Initial/change/equilibrium

Question 29

Kd, partition coefficient

Answer 29

Measures relative solubility of a solute between 2 solvents

Question 30

Kd equation

Answer 30

Concentration of organic solvent/concentration in water

Non-polar organic compounds=more soluble in organic solvents than in water, therefore Kd=>1

Question 31

Kp

Answer 31

Equil constant for gases

Question 32

Kp equation steps?

Answer 32

1) mole fraction of A, Xa=no. of moles in A/total moles in gas mixture
2) A’s partial pressure, Pa= Xa x P (P=total pressure)

Question 33

Partial pressure, p

Answer 33

Contribution a gas makes towards total pressure, P

Question 34

Kp equilibrium constant equation

Answer 34

Similar to Kc, but replace concentrations with partial pressures

Question 35

Kp units

Answer 35

Replace partial pressure value in Kp equation with the units

Question 36

K

Answer 36

E.g 0.09=k[0.1]⁰[0.3]²

k=0.09 aka 0.11