CHEMISTRY - Reversible Reactions

Question 1

what is a reversable reaction

Answer 1

a reaction in which where the products can react to form the original reactants,

so the reaction can go in both directs

Question 2

what is meant by “basic gas”

Answer 2

gas that dissolves in water to form alkali

Question 3

what is the haber process

Answer 3

when u do nitrogen + hydrogen to make ammonia

which is also reversable

Question 4

where do the raw materials for the haber process come from

Answer 4

nitrogen - from the air
hydrogen - from electrolysis of water OR cracking OR methane gas

Question 5

nitrogen is a fairly unreactive gas, what 3 things can be done to get the reaction to occur (to lower the activation energy)

Answer 5

-use iron catalyst
-increase temperature
-increase pressure

Question 6

what happens when you change the temperature of the haber process

Answer 6

increase temperature - higher rate but lower yield

decrease temperature - lower rate but higher yield

Question 7

what happens when you change the pressure of the haber process

Answer 7

increase pressure - higher yield

Question 8

the yield of ammonia from the Haber process is low at 28% even with conditions, what is done with the unreactive nitrogen and hydrogen

Answer 8

recycled

Question 9

how is ammonia removed from the final gas mixture

Answer 9

it is cooled, and ammonia turns into a liquid and then removed

Question 10

overtime, the yield of ammonia will begin to decrease, what is the cause of this decrease in yield and how would you fix it?

Answer 10

the catalyst becomes less effective

so replace the catalyst

Question 11

what is the gas test for oxygen and what is the result of the test

Answer 11

replace a glowing splint into the gas, if present the splint will relight.

Question 12

what is the gas test for ammonia and the result of the test

Answer 12

hold damp red litmus paper into the gas, litmus turns blue if present

Question 13

what is the gas test for carbon dioxide and the result

Answer 13

bubble the gas through limewater solution, limewater will turn milky, if present

Question 14

what is the gas test for hydrogen and the result

Answer 14

place a lit splint into the gas, gas will burn with a squeaky POP if present

Question 15

what is the symbol for ammonia and ammonium

Answer 15

Ammonia = NH3

ammonium = NH4

(the 3 and 4 are meant to be little)

Question 16

what is the contact process and explain it

Answer 16

when sulfuric acid is made in a three stage synthesis

stage 1 - production of sulfur dioxide from naturally occurring raw materials, (burning sulfur with oxygen)

stage 2 - sulfur dioxide is oxidised to sulfur trioxide (sulfur dioxide + oxygen) temperature has to be at 450 degrees, pressure has to be at 1-2 atmosphere and catalyst is vanadium oxide

stage 3 - conversion of sulfur trioxide to sulfuric acid (sulfur trioxide + water)

Question 17

how do you obtain sulfur dioxide

Answer 17

sulfur + oxygen

Question 18

what are the 3 conditions needed for stage 2 of the contact process

Answer 18

-temperature has to be at 450 degrees for a good yield
-catalyst used will be vanadium oxide
-pressure has to be 1-2 atmospheres

Question 19

the conversion of sulfur trioxide to sulfuric acid is highly exothermic and hazardous , why? and how can this be overcome?

Answer 19

could be very dangerous for workers as a mist of sulfuric acid is formed

to overcome this hazard,
sulfur trioxide is passed into concentrated sulfuric acid which only contains 2% water. the sulfur trioxide reacts with the sulfuric acid to form a substance called oleum.

and then the water is also passed into the concentrated sulfuric acid to maintain the concentration of the acid at 98%

Question 20

what is the use of concentrated sulfuric acid?

Answer 20

used as a powerful dehydrating agent (removes water from substances)

Question 21

what is the majority of the sulfuric acid that is produced from the contact process used for

Answer 21

to make fertilisers

Question 22

how is sulfuric acid used to make fertilisers

Answer 22

sulfuric acid + ammonia = ammonia sulfate

Question 23

ammonium salts are all soluble, why is this an essential property of a fertiliser?

Answer 23

plants can absorb them through their roots.

Question 24

what is eutrophication and explain it

Answer 24

environmental problem caused by the fertilisers being washed off into streams, causing rapid plant growth for plants in the water, then the surface of water will be covered in plants, the lack of sunlight causes plants living below the surface to die and bacteria use up the oxygen in the water to decompose the dead plant matter. The lack of oxygen in the water causes the aquatic animals to die.

Question 25

what are 2 advantages and 2 disadvantages of using fertiliser

Answer 25

advantage - increase crop yield, health quality

disadvantage - eutrophication, stomach cancer

Question 26

why arent we able to stop use of artificial fertiliser

Answer 26

as population increases, food demands increases, and natural fertilisers cant provide enough food

Question 27

if the forward reaction is exothermic then what is the reverse reaction?

Answer 27

endothermic

Question 28

what produces ammonia

Answer 28

nitrogen gas (from the air)
and hydrogen gas (from natural gas) react together to produce ammonia

Question 29

what is the test for ammonium ions (NH4 + )

Answer 29

add sodium hydroxide solution, test teh gas with a damp red litmus

the ammonium ions convert to ammonia gas which turns the damp red litmus paper blue

Question 30

what is the bad thing about operating at higher pressures

Answer 30

its expensive
and more risk of explosions