5.1 Rates, Equilibrium And pH

Question 1

Define reaction rate

Answer 1

Change in the amount of product or reactants per unit time

Question 2

Define Order of reaction

Answer 2

Order with respect to a particular reactant tells you how the reactant’s concentration affects the rate .
(These can only be found from experiment.)

Question 3

Overall order definition

Answer 3

the sum of the individual orders for each reactant

Question 4

The rate constant, k, definition

Answer 4

a constant of proportionality in the rate equation that can be calculated from the orders and rates of reaction

Question 5

Half Life definition

Answer 5

The time taken for half the reactants to be used up

Question 6

Rate-determining step

Answer 6

The slowest step in a multi-step reaction

Question 7

How do you find orders?

Answer 7

From concentration-time and concentration-rate graphs

Conc-Time
Downward constant slope: 0th Order
Curved: 1st Order

Conc-rate
Flat line: 0th order
positive constant slope through origin: 1st Order
Upwards curve: 2nd Order

Question 8

How do you create a rate equation from orders?

Answer 8

rate = k[A]^m[B]^n

m and n are the orders of reactants A and B

Question 9

How do you find the half life for a 1st order reaction?

Answer 9

1st order has a constant half life (Independent of concentration)
It’s the time it takes to half the reactants concentrations

Question 10

How do you find rate constant with half life?

Answer 10

k = ln2/t1/2

t1/2=Halflife

Question 11

What are the techniques and procedures used to
investigate reaction rates by the initial rates
method and by continuous monitoring, including
use of colorimetry

Answer 11

For reactions with acids or bases measure pH changes by doing titrations or using a pH meter
•If a product of the reaction is a gas, measure the volume of gas produced at regular time intervals
•Volume of gas is proportional to moles of gas
•So it can be used to measure the amount of product produced
•Colorimetry is used if the products or reactants are coloured
○Reactants are mixed and timer is started
○Light absorbance at a particular wavelength is measured at set time intervals

Question 12

Can you predict
a rate equation that is consistent with the
rate-determining step

Answer 12

yes

Question 13

Can you predict
a rate equation that is consistent with the
rate-determining step

Answer 13

Maybe