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gcse science C4 - D

specific for ocr gateway additonal science B.

QuestionAnswer
what 4 things does the haber process use? -an iron catalyst -high pressure -a temperature of 450 -a recycling system for unreacted nitrogen and hydrogen
what is the word equation for the haber process? nitrogen + hydrogen = ammonia
what is the balanced symbol equation for the haber process? N2 + 3H2 = 2NH3
what is the forward reaction for the haber process? nitrogen + hydrogen - ammonia
what is the backward reaction for the haber process? nitrogen + hydrogen - ammonia
what does a reversible reaction mean? reactions that go in both directions at the same time
why can't the percentage yield for the reaction be 100%? because the reaction is reversible
what is an advantage and disadvantage of using a higher pressure? -increases the percentage yield -high pressures cost more
what is an advantage and disadvantage of using a high temperature? -makes the reaction go faster -decreases the percentage yield
what is an advantage and disadvantage of using 450 (the optimum temperature)? -yield is made faster -yield isn't as good
what is an advantage of using a catalyst? makes the reaction go faster
what 7 factors affect the cost of making ammonia? -labour -reactants -recycling -high pressure -energy -reaction rate -pollution control
how does labour affect the cost of making ammonia? chemical plants are heavily automated and need few people to operate them
how does reactants affect the cost of making ammonia? hydrogen is made from natural gas or by cracking oil - which costs money. nitrogen has to be cleaned, dried and compressed
how does recycling affect the cost of making ammonia? means that money isn't wasted. unreacted chemicals are recycled back into the reaction vessel
how does high pressure affect the cost of making ammonia? makes the reaction work better but costs more for the pipes and fittings made from stronger steel. lower optimum pressure is used as high pressure costs more and needs compressors and pumps.
how does energy affect the cost of making ammonia? works at an optimum temperature of 450, which means higher energy costs for the fuel, as well as lower yields. the increase in rate compensates.
how does reaction rate affect the cost of making ammonia? the faster the reaction, the more product is made from the same equipment, so the cheaper it is
how does pollution control affect the cost of making ammonia? reducing pollution is expensive
what does the term optimum conditions mean? chemical plants work at the conditions that produce the highest percentage yield for a reaction, most cheaply
give an explanation of how high temperatures affect the costs. optimum temperature of 450 means higher energy costs and lower yields, but the increase in rate compensates. the plant produces more ammonia in a day at this temperature than it would at lower temperatures.
Created by: jirwin
 

 



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