Chemical Industry

Question 1

calculating order of reaction

Answer 1

The number on the outside of the bracket refers to the ‘order with respect to..’ and the sum of the indices of all brackets is the overall order

Question 2

effect on rate

Answer 2

Zero order = 0 effect
First order = double concentration, double rate
Second order = double concentration, quadruple rate

Question 3

nitrogen reactivity

Answer 3

Lack of reactivity is due to triple covalent bonds in diatomics, resulting in a high bond enthalpy

Question 3

factors that can be measured to deduce order

Answer 3

Volumes of gasses evolved
Mass changes
pH
Colorimetry
Chemical analysis such as titration

Question 4

glowing splint in dinitrogen monoxide

Answer 4

it will relight because the splint provides enough energy to decompose dinitrogen monoxide into nitrogen and oxygen

Question 5

property of NO

Answer 5

Colourless
Insoluble
Turns universal indicator neutral, will turn brown very quickly in test tube if slightly exposed to oxygen due to being incredibly reactive to nitrogen dioxide

Question 6

property of NO2

Answer 6

Brown
Soluble only in cold water
Turns indicator orange, due to acidity

Question 7

property of N2O

Answer 7

Colourless
Slightly soluble in cold water
Neutral universal indicator, similar to nitrogen monoxide

Question 8

define rate

Answer 8

how quickly a quantity of something changes

Question 9

Rate of reaction

Answer 9

the rate at which reactants are converted into products

Question 10

rate constant

Answer 10

the value of K, must always say at what temperature the changes were made

Question 11

Measuring the volumes of gases evolved

Answer 11

Volume produced can be collected in a gas syringe

Question 12

Measuring mass changes

Answer 12

Record the mass lost from the reaction

Question 13

Ph

Answer 13

Monitor the pH of the reaction mixture

Question 14

Colorimetry

Answer 14

use a colorimeter to measure the change in colour of the reaction

Question 15

Chemical analysis and titration

Answer 15

samples of mixture are taken at regular intervals, quenching involved (stopping the reaction in the sample before analysis)

Question 16

Initial rates

Answer 16

draw a tangent to the curve at t=0 and measure the gradient

Question 17

Progress method

Answer 17

shows how the concentration of a reaction changes as a reaction proceeds, the gradient of each tangent gives the rate of reaction for the concentration of that substance. Then use initial rate method to plot graph of initial rate against concentration to determine order

Question 18

Half life

Answer 18

if it is constant the reaction is first order

Question 19

Reciprocal of reaction time as a measure of the rate

Answer 19

average rate is directly proportional to the reciprocal to 1 over time (if 1 remains constant). Plot a graph of the reciprocal against the concentration of the other substance (unconstant.)

Question 20

First order

Answer 20

initial rate is directly proportional to concentration

Question 21

second order

Answer 21

initial rate is directly proportional to concentration squared

Question 22

zero order

Answer 22

rate not changing

Question 23

by product and co product

Answer 23

the product of the unwanted side reaction
produced with the expected main amount

Question 24

Change in rate if temperature is increased:

Answer 24

Rate equations for the two temps
Equations for K1 and K2 using Arrhenius
Calculate the values for the rest of the equation

Question 25

changing the conc and pressure

Answer 25

Kc REMAINS CONSTANT.
They alter the composition of equilibrium mixtures but not the value of Kc itself because proportions of reactants and products alter themselves to keep the ratio in Kc expression the same.

Question 26

Changing the temperature

Answer 26

Temperature will change Kc.
EXAMPLES: an increase in temperature to the surroundings will cause the reaction to favour the endothermic direction of the system because there will be more energy to take in.

Question 27

Catalyst

Answer 27

Does not affect the position of equilibrium or Kc.
Only alters the rate at which equilibrium is obtained.
Does not affect the composition of the equilibrium mixture.

Question 28

rate determining step

Answer 28

The slowest step in the mechanism

Question 29

Using the rate equation in regards to RDS

Answer 29

The substances in the rate equation are in the RDS
Those not in the rate equation are not in the RDS
The power of the order is the number of moles in the RDS

Question 30

If the energy barrier is large

Answer 30

the reacting species (either a single species or pair of colliding species) have enough energy to pass over it and the rate of conversion of reactants to products is low

Question 31

If RDS is the first step

Answer 31

every step afterwards will happen very quickly

Question 32

If RDS is the last step

Answer 32

the previous step will happen quickly and form a bottleneck because they are waiting for the product to form

Question 33

how to remove a gaseous by product from the desired product

Answer 33

condense the desired product

Question 34

define half life

Answer 34

the time taken for half of a certain reactant to get used up

Question 35

presence of nitrite ions with iron 2 plus ions

Answer 35

the nitrite ions will oxidise the Fe2+ ions so the test is not reliable if the solution has nitrite ions