chemical industry

Question 1

what does the rate of reaction measure

Answer 1

the rate of reactant→product conversion

Question 2

formula for rate

Answer 2

rate = amount of reactant used or product made / time

Question 3

use of rate equation

Answer 3

can be used to calculate the rate of reaction from concentrations and a known constant for a given temperature

Question 4

rate equation

Answer 4

rate = k[A]^a [B]^b
[A] [B] = concentration of reactants
a b = orders of reactant

Question 5

orders of reaction meaning

Answer 5

the power to which a concentration is raised to in the rate equation

Question 6

zero order meaning

Answer 6

changes in concentration has no effect on rate

Question 7

first order meaning

Answer 7

changes in concentration has a proportional change on the rate
e.g. if [A] doubles, rate doubles

Question 8

second order meaning

Answer 8

changes in concentration has a squared proportional change on the rate
e.g. if [A] doubles, rate quadruples

Question 9

features of rate constant - k

Answer 9

• only fixed at a particular temperature
• larger value of K, the faster the reaction

Question 10

finding rate on a concentration time graph

Answer 10

rate is found by taking the gradient

Question 11

zero order on a concentration time graph

Answer 11

\
diagonal line from top to bottom

Question 12

zero order on a rate concentration graph

Answer 12

_
horizontal line, as changing concentration doesn’t affect rate

Question 13

first order on a concentration time graph

Answer 13

slight curved slope doing down as time increases, eventually plateaus (not very steep)

Question 14

first order on a rate concentration graph

Answer 14

/
straight diagonal line going up, as changing concentration changes rate equally

Question 15

second order on a concentration time graph

Answer 15

curved slope doing down as time increases, eventually plateaus (steep)

Question 16

second order on a rate concentration graph

Answer 16

curved line going up
changing concentration changes the rate squared

Question 17

half life definition

Answer 17

the time it takes for half of the reactant to be used up

Question 18

half life of zero order

Answer 18

half life decreases

Question 19

half life of first order

Answer 19

half life is constant

Question 20

half life of second order

Answer 20

half if increases

Question 21

formula to calculate half life from rate constant

Answer 21

k = ln2 / half life

Question 22

arrhenius equation for graphs

Answer 22

lnK = (-Ea/R) 1/T + lnA

Question 23

arrhenius equation meaning

Answer 23

k = rate constant
A = arrhenius constant
e = exponential (on calculator)
Ea = activation energy
R = gas constant
T = temperature (in K)

Question 24

what is the rate determining step

Answer 24

the slowest step in a multi-step reaction
the whole reaction rate depends on how quick the rds is

Question 25

features of the rate equation

Answer 25

- reactants that appear in the rate equation affect the rate reaction - these reactants (or substances derived from them) must appear in the rate determining step

Question 26

what are reversible reactions

Answer 26

reactions that can go forward and backward

Question 27

features of a reversible reaction

Answer 27

- dynamic equilibrium reached when rate of forward = rate of backward - concentration of substance remains constant - only occurs in closed systems

Question 28

what affects value of Kc

Answer 28

only temperature

Question 29

temperature affect on Kc

Answer 29

- changing the temperature will change equilibrium concentrations - if temperature change causes equilibrium to shift to right, Kc will increase - if temperature change causes equilibrium to shift left, Kc will decrease

Question 30

Kc expression

Answer 30

[products] / [reactants]

Question 31

what is Kc

Answer 31

the equilibrium constant

Question 32

Kc expression of 2A + B <==> 2C + D

Answer 32

Kc = [C]^2 [D] / [A]^2 [B]

Question 33

features of nitrogen

Answer 33

- diatomic molecule - in group 5 - 1s2 2s2 2p3 - forms a covalent triple bond (very difficult to break and so nitrogen is an unreactive gas at room temperature)

Question 34

common nitrogen molecules

Answer 34

- ammonia (NH3) - ammonium (NH4+) - nitrogen monoxide (NO) - dinitrogen oxide (N2O) - nitrogen dioxide (NO2)

Question 35

features of ammonia

Answer 35

- NH3 - formed by N2 + H2 - formed in Haber process - Nitrogen shares 3 of its valence electrons with hydrogen and a lone pair of electrons remain - due to lone pair, ammonia can form hydrogen bonds with water so it is very stable - ammonia can form dative covalent bonds using lone pair, e.g. to form ammonium ion

Question 36

raw materials meaning

Answer 36

chemical companies will try and source raw materials that are cheap and widely available