5.1.1/2 How Far and How Fast (completed)

Question 1

How can you monitor the rate of reaction?

Answer 1

Volume of gas produced per second
Change in intensity of colour
Change in pH
How quickly a reactant disappears
How quickly a precipitate forms

Question 2

What is the equation for rate of reaction?

Answer 2

Change in concentration / time

Mol dm-3 s-1

Question 3

What are the three orders of reaction and what do they mean?

Answer 3

Zero order - the rate is independent of concentration of reactant

First order - the rate is directly proportional to the concentration of reactant

Second order - the rate is directly proportional to the concentration of reactant squared

Question 4

On a concentration time graph how can you identify a second order reaction?

Answer 4

The half life is variable, for first order the half life is constant

Question 5

Draw a concentration time graph for each order reaction

Answer 5

Zero order negative linear
First order 1/x ish
Second order 1/x^2 ish

Question 6

What is the half life?

Answer 6

The time it takes for the concentration of a reactant to reduce by one half

Question 7

Draw a rate concentration graph for each order reactant

Answer 7

Zero order y=4
First order positive linear from origin
Second order quadratic from origin

Question 8

What is the initial rates method for finding orders of reaction?

Answer 8

Measure the gradient at time = 0 to estimate initial rate of reaction for three different experiments and go from there

Question 9

What is the rate equation for this reaction?

A + B -> C + D

Answer 9

Rate = k [A]^a[B]^b
A is ‘a’ order
B is ‘b’ order

Overall order is a + b

Question 10

What is the rate constant?

Answer 10

It is different for each reaction and is constant at a particular temperature and always increases with temperature
The units change with each equation

Question 11

What is the equation of the rate constant with half-life in?

Answer 11

k = ln2 / t

Question 12

What is the rate determining step?

Answer 12

The slowest step

This governs the overall rate of the reaction 

Question 13

What are the tips for proposing mechanisms with rate determining steps?

Answer 13

• Make RDS First equation
• Put everything in rate equation to make a super particle
• Add everything else
• Write the products

Question 14

What is the Arrhenius equation?

Answer 14

In the formula book with the logarithmic form

Question 15

What is the gradient and y intercept of an Arrhenius plot?

Answer 15

m = -Ea/ R
c = lnA

Question 16

How do you write an equation for the equilibrium constant?

Answer 16

Kc = concentration of products to the power of moles
————————————————
Concentration of reactants to the power of moles

Question 17

How does temperature affect the equilibrium constant?

Answer 17

Endothermic reaction positive correlation

Exothermic reaction negative correlation

Question 18

How does pressure affect equilibrium constant?

Answer 18

It doesn’t

Question 19

What is a heterogeneous equilibrium?

Answer 19

Some reactants and products are solid and some gas

Remove the solid and only use the gases in the Kc equation

Question 20

How do you workout the mole fraction of gas?

Answer 20

number of moles of gas X
————————————
total number of moles

Question 21

How do you workout partial pressure?

Answer 21

Mole fraction x total pressure

Question 22

What is Kp and how do you work it out?

Answer 22

It is the equilibrium constant that applies to gaseous systems and it is similar to Kc but uses partial pressure in place of concentration

Question 23

What must you not include in Kp?

Answer 23

Solids and pure liquids