CHEMISTRY - Reversible Reactions Flashcards
what is a reversable reaction
a reaction in which where the products can react to form the original reactants,
so the reaction can go in both directs
what is meant by “basic gas”
gas that dissolves in water to form alkali
what is the haber process
when u do nitrogen + hydrogen to make ammonia
which is also reversable
where do the raw materials for the haber process come from
nitrogen - from the air
hydrogen - from electrolysis of water OR cracking OR methane gas
nitrogen is a fairly unreactive gas, what 3 things can be done to get the reaction to occur (to lower the activation energy)
-use iron catalyst
-increase temperature
-increase pressure
what happens when you change the temperature of the haber process
increase temperature - higher rate but lower yield
decrease temperature - lower rate but higher yield
what happens when you change the pressure of the haber process
increase pressure - higher yield
the yield of ammonia from the Haber process is low at 28% even with conditions, what is done with the unreactive nitrogen and hydrogen
recycled
how is ammonia removed from the final gas mixture
it is cooled, and ammonia turns into a liquid and then removed
overtime, the yield of ammonia will begin to decrease, what is the cause of this decrease in yield and how would you fix it?
the catalyst becomes less effective
so replace the catalyst
what is the gas test for oxygen and what is the result of the test
replace a glowing splint into the gas, if present the splint will relight.
what is the gas test for ammonia and the result of the test
hold damp red litmus paper into the gas, litmus turns blue if present
what is the gas test for carbon dioxide and the result
bubble the gas through limewater solution, limewater will turn milky, if present
what is the gas test for hydrogen and the result
place a lit splint into the gas, gas will burn with a squeaky POP if present
what is the symbol for ammonia and ammonium
Ammonia = NH3
ammonium = NH4
(the 3 and 4 are meant to be little)
what is the contact process and explain it
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)
how do you obtain sulfur dioxide
sulfur + oxygen
what are the 3 conditions needed for stage 2 of the contact process
-temperature has to be at 450 degrees for a good yield
-catalyst used will be vanadium oxide
-pressure has to be 1-2 atmospheres
the conversion of sulfur trioxide to sulfuric acid is highly exothermic and hazardous , why? and how can this be overcome?
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%
what is the use of concentrated sulfuric acid?
used as a powerful dehydrating agent (removes water from substances)
what is the majority of the sulfuric acid that is produced from the contact process used for
to make fertilisers
how is sulfuric acid used to make fertilisers
sulfuric acid + ammonia = ammonia sulfate
ammonium salts are all soluble, why is this an essential property of a fertiliser?
plants can absorb them through their roots.
what is eutrophication and explain it
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.
what are 2 advantages and 2 disadvantages of using fertiliser
advantage - increase crop yield, health quality
disadvantage - eutrophication, stomach cancer
why arent we able to stop use of artificial fertiliser
as population increases, food demands increases, and natural fertilisers cant provide enough food
if the forward reaction is exothermic then what is the reverse reaction?
endothermic
what produces ammonia
nitrogen gas (from the air)
and hydrogen gas (from natural gas) react together to produce ammonia
what is the test for ammonium ions (NH4 + )
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
what is the bad thing about operating at higher pressures
its expensive
and more risk of explosions
