the chemical industry

Question 1

What is the definition of reaction rate?

Answer 1

The change in the amount of reactants or products per time unit.

Question 2

What are the ways of following the progress of a reaction?

Answer 2

pH measurement
Gas volume
Loss of mass
Colorimetry 
Titration

Question 3

How do you work out rate from a concentration-time graph?

Answer 3

Gradient = change in y/change in x

Gradient represents rate

Question 4

what assumptions do you make in the initial rate method of measuring rate?

Answer 4

• concentration of the other reactants isn’t changing significantly
• temperature stays constant
• the reaction has not proceeded too far

Question 5

what is the rate equation?

Answer 5

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

Question 6

what does an order of reaction of 2 represent in terms of [A]?

Answer 6

[A] squared

Question 7

define half life

Answer 7

the half life is the amount of time it takes for half of the reactants to be used up.

Question 8

how does a zero order reaction present in terms of half life?

Answer 8

half life decreases with time

Question 9

how does half life change for a 1st order reaction?

Answer 9

it remains constant

Question 10

how does half life change during a 2nd order reaction?

Answer 10

it increases with time

Question 11

how can you calculate the rate constant from half life?

Answer 11

k= ln2/half life

Question 12

what must happen for a reaction to take place?

Answer 12

• particles must collide
• have energy ≥ activation enthalpy
• have the right orientation

Question 13

how does increasing temperature affect the rate constant?

Answer 13

a higher temperature results in a higher rate constant

Question 14

define order of reaction

Answer 14

order of reaction shows the number of molecules of that reactant which are involved in the rate determining step.

Question 15

what economic considerations are there within the chemical industry?

Answer 15

• raw materials
• overheads/fixed costs
• fuel/energy
• disposal costs

Question 16

what alters the magnitude of Kc?

Answer 16

temperature changes; if the change in position of equilibrium results in more product, Kc is larger.

Question 17

why is ammonia soluble?

Answer 17

can form hydrogen bonds with other molecules

Question 18

what is a test for ammonium compounds?

Answer 18

• add NaOH + heat gently, ammonia gas should be evolved.

- damp litmus -> blue

Question 19

how do you test for Nitrate(V)?

Answer 19

warm solution with NaOH + add aluminium foil or devarda’s alloy.
in the presence of an alkali, aluminium reduces nitrate -> ammonia gas.

Question 20

describe the appearance and characteristics of the following oxides of nitrogen, NO, N2O and NO2

Answer 20

NO= colourless
N2O= sweet smell, colourless
NO2= brown, sharp odour, toxic

Question 21

what are the equations for the conversion of N2 into NH3, and the conversion of NH3 into NH4?

Answer 21

N2 + 3H2 -> 2NH3

NH3 + H+ -> NH4+

Question 22

what are the equations for the conversion of NH4+ into NO2-, and the conversion of NO2- into NO3-?

Answer 22

NH4+ +O2 -> NO2- +4H+ +2e-

NO2+ + H2O -> NO3- + 2H+ + 2e-

Question 23

what is the equation for the conversion of NO3 into N2?

Answer 23

2NO3+ 12H+ + 10e- -> N2 + 6H2O