Reversible Reactions, Equilibrium, Haber Process and Contact Process

1. A reversible reaction reaches dynamic equilibrium in a sealed container.

Which statement is correct?

A The forward reaction stops and the reverse reaction continues.
B The reverse reaction stops and the forward reaction continues.
C The forward and reverse reactions occur at the same rate.
D The amounts of reactants and products must be equal.

2. Which condition is required for dynamic equilibrium to be established?

A an open system
B a closed system
C a catalyst only
D a very low temperature only

3. In a reversible reaction at equilibrium, the forward reaction is exothermic.

What happens when temperature is increased?

A equilibrium shifts towards products
B equilibrium shifts towards reactants
C forward and reverse reactions both stop
D concentration of products must increase

4. In a reversible reaction, the forward reaction is endothermic.

What happens when temperature is decreased?

A equilibrium shifts in the endothermic direction
B equilibrium shifts in the exothermic direction
C activation energy becomes zero
D catalyst stops working

5. Which statement about Le Chatelier’s principle is correct?

A The equilibrium shifts to increase the change imposed.
B The equilibrium shifts to oppose the change imposed.
C The equilibrium always shifts to the side with more moles of gas.
D The equilibrium always shifts to the exothermic side.

6. A reversible reaction is shown.

A(g) + 2B(g) ⇌ C(g)

What happens when pressure is increased?

A equilibrium shifts left because there are more gas molecules on the left
B equilibrium shifts right because there are fewer gas molecules on the right
C equilibrium does not shift because all substances are gases
D equilibrium shifts left because pressure favours reactants

7. A reversible reaction is shown.

2X(g) ⇌ Y(g) + Z(g)

What happens when pressure is increased?

A equilibrium shifts right
B equilibrium shifts left
C equilibrium does not shift
D reaction stops

8. A reversible reaction is shown.

N2(g) + 3H2(g) ⇌ 2NH3(g)

Which change increases the equilibrium yield of ammonia?

A lower pressure
B higher pressure
C higher temperature only
D removing nitrogen

9. In the Haber process, the forward reaction is exothermic.

N2(g) + 3H2(g) ⇌ 2NH3(g)

Which temperature gives the highest equilibrium yield of ammonia?

A very low temperature
B moderate temperature
C high temperature
D temperature has no effect

10. Why is a very low temperature not used in the Haber process, even though it gives a higher equilibrium yield?

A the reaction becomes too slow
B ammonia decomposes instantly
C nitrogen becomes unreactive permanently
D catalyst is used up faster

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

11. Why is high pressure used in the Haber process?

A it shifts equilibrium to the side with more gas molecules
B it shifts equilibrium to the side with fewer gas molecules
C it makes the reaction endothermic
D it removes the need for a catalyst

12. Why is an extremely high pressure not used in the Haber process?

A it lowers ammonia yield
B it makes nitrogen and hydrogen stop reacting
C it is expensive and dangerous
D it changes ammonia into sulfur trioxide

13. Which catalyst is used in the Haber process?

A vanadium(V) oxide
B iron
C nickel
D platinum

14. Which conditions are commonly used in the Haber process?

A 450°C, 200 atm, iron catalyst
B 100°C, 1 atm, vanadium(V) oxide catalyst
C 900°C, 2 atm, nickel catalyst
D room temperature, 1 atm, no catalyst

15. What is the main raw material source of nitrogen for the Haber process?

A crude oil
B air
C limestone
D seawater

16. What is a common source of hydrogen for the Haber process?

A air
B cracking of ammonia
C natural gas/steam reforming
D limestone decomposition

17. Why is ammonia removed from the equilibrium mixture in the Haber process?

A to shift equilibrium towards ammonia formation
B to shift equilibrium towards nitrogen and hydrogen
C to poison the catalyst
D to decrease the rate of reaction

18. Unreacted nitrogen and hydrogen are recycled in the Haber process.

Why?

A to reduce waste and increase overall conversion
B to lower the boiling point of ammonia
C to make the reaction irreversible
D to remove the iron catalyst

19. In the Haber process, what happens when ammonia is liquefied and removed?

A equilibrium shifts left
B equilibrium shifts right
C pressure becomes zero
D nitrogen and hydrogen stop reacting

20. Which statement about the iron catalyst in the Haber process is correct?

A it increases the equilibrium yield of ammonia
B it speeds up both forward and reverse reactions equally
C it shifts equilibrium to the product side
D it is consumed during the reaction

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

21. A reversible reaction is shown.

2SO2(g) + O2(g) ⇌ 2SO3(g)

The forward reaction is exothermic.

Which change increases the equilibrium yield of SO3?

A increasing temperature
B decreasing pressure
C increasing pressure
D adding a catalyst only

22. In the Contact process, why is a temperature of about 450°C used?

A it gives a complete yield at maximum rate
B it is a compromise between rate and equilibrium yield
C it prevents sulfur dioxide from reacting
D it makes the reaction endothermic

23. Which catalyst is used in the Contact process?

A iron
B vanadium(V) oxide
C nickel
D aluminium oxide

24. Which equation represents the key reversible reaction in the Contact process?

A N2 + 3H2 ⇌ 2NH3
B 2SO2 + O2 ⇌ 2SO3
C SO3 + H2O → H2SO4
D S + O2 → SO2

25. Why is high pressure not usually necessary in the Contact process?

A pressure has no effect because gases are absent
B atmospheric/moderate pressure already gives a high yield and high pressure is expensive
C high pressure shifts equilibrium to sulfur dioxide
D high pressure destroys vanadium(V) oxide

26. What happens to the equilibrium position in the Contact process when pressure is increased?

2SO2(g) + O2(g) ⇌ 2SO3(g)

A shifts left
B shifts right
C no change
D both reactions stop

27. Which raw material is used to make sulfur dioxide in the Contact process?

A sulfur or sulfide ores
B nitrogen from air only
C ammonia
D sodium chloride

28. Why is sulfur trioxide not usually reacted directly with water in the industrial manufacture of sulfuric acid?

A the reaction is too slow
B it forms ammonia
C it produces a dangerous mist of sulfuric acid
D sulfur trioxide is insoluble in water and unreactive

29. What is formed when sulfur trioxide is absorbed in concentrated sulfuric acid?

A oleum
B ammonia
C sulfur dioxide
D hydrogen sulfide

30. Oleum is diluted with water to produce which substance?

A nitric acid
B hydrochloric acid
C sulfuric acid
D sulfurous acid

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

31. A reversible reaction is shown.

PCl5(g) ⇌ PCl3(g) + Cl2(g)

The forward reaction is endothermic.

Which conditions favour the formation of PCl5?

A high temperature and high pressure
B low temperature and high pressure
C high temperature and low pressure
D low temperature and low pressure

32. A reversible reaction is shown.

H2(g) + I2(g) ⇌ 2HI(g)

What is the effect of increasing pressure?

A equilibrium shifts left
B equilibrium shifts right
C no shift in equilibrium position
D iodine becomes a catalyst

33. A reversible reaction is shown.

CO(g) + 2H2(g) ⇌ CH3OH(g)

The forward reaction is exothermic.

Which conditions favour the highest equilibrium yield of methanol?

A low temperature and high pressure
B high temperature and low pressure
C high temperature and high pressure
D low temperature and low pressure

34. A catalyst is added to a reversible reaction at equilibrium.

What happens?

A equilibrium shifts to products
B equilibrium shifts to reactants
C equilibrium is reached faster but final equilibrium position is unchanged
D equilibrium yield increases only for exothermic reactions

35. Which statement about equilibrium concentration is correct?

A At equilibrium, concentrations of reactants and products are always equal.
B At equilibrium, concentrations remain constant because forward and reverse rates are equal.
C At equilibrium, concentration of products must be greater than reactants.
D At equilibrium, particles stop colliding.

36. A closed container contains brown NO2 and colourless N2O4.

2NO2(g) ⇌ N2O4(g)

The forward reaction is exothermic.

What happens when the container is cooled?

A brown colour becomes darker because more NO2 forms
B brown colour becomes paler because more N2O4 forms
C pressure increases and equilibrium shifts to NO2
D no change occurs because equilibrium stops at low temperature

37. For the same equilibrium:

2NO2(g) ⇌ N2O4(g)

What happens when pressure is increased?

A more NO2 forms
B more N2O4 forms
C no shift occurs
D both gases disappear

38. A reversible reaction is shown.

A(g) ⇌ 2B(g)

The forward reaction is endothermic.

Which change favours B?

A decrease temperature and increase pressure
B increase temperature and decrease pressure
C decrease temperature and decrease pressure
D increase temperature and increase pressure

39. A reversible reaction is shown.

2A(g) + B(g) ⇌ C(g) + D(g)

The forward reaction is exothermic.

Which change favours reactants?

A increase pressure and decrease temperature
B decrease pressure and increase temperature
C increase pressure and increase temperature
D decrease pressure and decrease temperature

40. A reversible reaction is shown.

A(g) + B(g) ⇌ C(g) + D(g)

The forward reaction is exothermic.

Which change affects the equilibrium position?

A increasing pressure
B decreasing pressure
C increasing temperature
D adding a catalyst

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

41. In an equilibrium mixture, the rate of the forward reaction is 15 mol/dm3/s.

What is the rate of the reverse reaction?

A 0 mol/dm3/s
B 7.5 mol/dm3/s
C 15 mol/dm3/s
D greater than 15 mol/dm3/s

42. At equilibrium, a reaction mixture contains mostly reactants.

Which statement is correct?

A The forward reaction has stopped.
B The reverse reaction has stopped.
C The equilibrium position lies to the reactant side.
D The reaction cannot be reversible.

43. A reversible reaction is at equilibrium. More reactant is added.

What happens immediately after the change?

A forward rate increases
B reverse rate increases first
C both rates become zero
D equilibrium cannot be restored

44. A reversible reaction is at equilibrium. Some product is removed.

Which statement is correct?

A equilibrium shifts to make more product
B equilibrium shifts to make more reactant
C both forward and reverse reactions stop
D catalyst is destroyed

45. Which change increases both the rate and the equilibrium yield of ammonia in the Haber process?

A increasing temperature
B increasing pressure
C removing the catalyst
D decreasing pressure

46. Which change increases rate but decreases equilibrium yield of ammonia in the Haber process?

A increasing temperature
B decreasing temperature
C increasing pressure
D removing ammonia

47. Which statement explains the compromise temperature in the Haber process?

A Low temperature gives high yield but slow rate; high temperature gives faster rate but lower yield.
B Low temperature gives low yield and slow rate; high temperature gives high yield and fast rate.
C Temperature has no effect on yield but affects rate.
D High temperature gives high yield because the reaction is exothermic.

48. Which statement explains the compromise pressure in the Haber process?

A Low pressure gives high yield but is expensive.
B High pressure gives higher yield and faster rate but is expensive and dangerous.
C Pressure affects rate only, not yield.
D High pressure lowers ammonia yield because there are fewer gas molecules on the product side.

49. Which statement about the Contact process is correct?

A Lower temperature favours SO3 yield but rate becomes too slow.
B Higher temperature favours SO3 yield because the reaction is exothermic.
C A catalyst increases the equilibrium yield of SO3.
D Low pressure gives a higher SO3 yield because products have fewer gas molecules.

50. Which row correctly compares Haber process and Contact process?

	Haber process	Contact process
A	makes ammonia	makes sulfuric acid
B	uses V2O5 catalyst	uses iron catalyst
C	forward reaction is endothermic	forward reaction is endothermic
D	low pressure favours product	low pressure favours product

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

1. C

A wrong: In dynamic equilibrium, the forward reaction does not stop.
B wrong: The reverse reaction also does not stop.
C right: Dynamic equilibrium means forward and reverse reactions occur at the same rate.
D wrong: Concentrations stay constant, but they do not have to be equal.

2. B

A wrong: In an open system, substances can escape, so equilibrium may not be established.
B right: A closed system is needed so reactants and products remain in the container.
C wrong: A catalyst is not required for equilibrium.
D wrong: Equilibrium does not require very low temperature only.

3. B

A wrong: Higher temperature does not favour the exothermic forward reaction.
B right: Increasing temperature favours the endothermic reverse reaction, so equilibrium shifts towards reactants.
C wrong: Reactions continue at equilibrium.
D wrong: Product concentration usually decreases.

4. B

A wrong: Lower temperature does not favour the endothermic direction.
B right: Decreasing temperature favours the exothermic direction.
C wrong: Activation energy does not become zero.
D wrong: Catalyst does not stop working simply because temperature decreases.

5. B

A wrong: Equilibrium shifts to reduce, not increase, the imposed change.
B right: Le Chatelier’s principle says equilibrium shifts to oppose the change.
C wrong: Pressure changes favour fewer/more gas moles depending on the change.
D wrong: Temperature changes determine whether exothermic or endothermic direction is favoured.

6. B

Left side has 3 moles of gas.
Right side has 1 mole of gas.

A wrong: Increased pressure does not favour the side with more gas molecules.
B right: Increased pressure favours the side with fewer gas molecules, so equilibrium shifts right.
C wrong: Pressure can affect gaseous equilibria.
D wrong: Pressure does not automatically favour reactants.

7. C

Left side has 2 moles of gas.
Right side has 2 moles of gas.

A wrong: No side has fewer gas molecules.
B wrong: No side has fewer gas molecules.
C right: Increasing pressure causes no shift because gas moles are equal on both sides.
D wrong: Reaction does not stop.

8. B

A wrong: Lower pressure favours the side with more gas molecules, so less ammonia.
B right: Higher pressure favours ammonia because 4 gas moles become 2 gas moles.
C wrong: Higher temperature lowers ammonia yield because forward reaction is exothermic.
D wrong: Removing nitrogen shifts equilibrium left.

9. A

A right: Since ammonia formation is exothermic, very low temperature gives the highest equilibrium yield.
B wrong: Moderate temperature is used industrially as a compromise, not maximum yield.
C wrong: High temperature lowers equilibrium yield.
D wrong: Temperature does affect equilibrium yield.

10. A

A right: Very low temperature gives high yield but the reaction rate becomes too slow.
B wrong: Ammonia does not instantly decompose.
C wrong: Nitrogen does not become permanently unreactive.
D wrong: Catalyst is not used up faster.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

11. B

A wrong: High pressure favours fewer gas molecules, not more.
B right: Haber process goes from 4 gas moles to 2 gas moles, so high pressure favours ammonia.
C wrong: Pressure does not change exothermic/endothermic nature.
D wrong: Pressure does not remove need for catalyst.

12. C

A wrong: Extremely high pressure would increase yield, not lower it.
B wrong: Nitrogen and hydrogen do not stop reacting.
C right: Extremely high pressure is expensive and dangerous due to strong equipment and safety risks.
D wrong: Sulfur trioxide is unrelated.

13. B

A wrong: Vanadium(V) oxide is used in the Contact process.
B right: Iron is the Haber process catalyst.
C wrong: Nickel is used in hydrogenation, not Haber at O Level.
D wrong: Platinum is not the Haber catalyst.

14. A

A right: Haber process uses about 450°C, about 200 atm, and iron catalyst.
B wrong: These are not Haber conditions and V2O5 is Contact catalyst.
C wrong: Too high temperature and wrong catalyst.
D wrong: Too slow and low yield/rate.

15. B

A wrong: Crude oil is not the main nitrogen source.
B right: Nitrogen is obtained from air.
C wrong: Limestone is calcium carbonate.
D wrong: Seawater is not the nitrogen source.

16. C

A wrong: Air supplies nitrogen, not hydrogen.
B wrong: Ammonia is the product, not usual hydrogen source.
C right: Hydrogen is commonly obtained from natural gas by steam reforming.
D wrong: Limestone decomposition gives calcium oxide and carbon dioxide.

17. A

A right: Removing ammonia lowers its concentration, so equilibrium shifts right to make more ammonia.
B wrong: Removing product does not shift equilibrium towards reactants.
C wrong: It does not poison catalyst.
D wrong: It helps production, not decreases rate.

18. A

A right: Recycling unreacted N2 and H2 reduces waste and increases overall conversion.
B wrong: It does not lower ammonia boiling point.
C wrong: The reaction remains reversible.
D wrong: It does not remove catalyst.

19. B

A wrong: Removing ammonia does not shift left.
B right: Removing ammonia shifts equilibrium right to replace ammonia.
C wrong: Pressure does not become zero.
D wrong: Nitrogen and hydrogen keep reacting.

20. B

A wrong: Catalyst does not change equilibrium yield.
B right: Catalyst speeds up both forward and reverse reactions equally, so equilibrium is reached faster.
C wrong: It does not shift equilibrium.
D wrong: It is not consumed.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

21. C

A wrong: Forward reaction is exothermic, so increasing temperature lowers SO3 yield.
B wrong: Decreasing pressure favours the side with more gas molecules, reactants.
C right: Increasing pressure favours SO3 because gas moles decrease from 3 to 2.
D wrong: Catalyst does not change equilibrium yield.

22. B

A wrong: It does not give complete yield and maximum rate at the same time.
B right: 450°C is a compromise between good rate and good equilibrium yield.
C wrong: It allows sulfur dioxide to react at a useful rate.
D wrong: It does not make the reaction endothermic.

23. B

A wrong: Iron is Haber catalyst.
B right: Vanadium(V) oxide is used in the Contact process.
C wrong: Nickel is not the Contact process catalyst.
D wrong: Aluminium oxide is not the catalyst here.

24. B

A wrong: This is Haber process.
B right: 2SO2 + O2 ⇌ 2SO3 is the key reversible reaction in Contact process.
C wrong: This is a later step, not the key reversible equilibrium.
D wrong: This makes sulfur dioxide, but it is not the main reversible equilibrium.

25. B

A wrong: Gases are present, so pressure has an effect.
B right: Moderate/atmospheric pressure already gives high yield; high pressure costs too much for limited extra benefit.
C wrong: High pressure shifts towards SO3, not SO2.
D wrong: High pressure does not destroy V2O5.

26. B

Left side has 3 moles of gas.
Right side has 2 moles of gas.

A wrong: Increased pressure does not favour the side with more gas molecules.
B right: Increased pressure favours SO3.
C wrong: Gas moles are not equal, so pressure affects equilibrium.
D wrong: Reactions do not stop.

27. A

A right: Sulfur dioxide is made by burning sulfur or roasting sulfide ores.
B wrong: Nitrogen is for Haber process.
C wrong: Ammonia is made in Haber process.
D wrong: Sodium chloride is used for chlorine/sodium hydroxide manufacture.

28. C

A wrong: The reaction is not too slow.
B wrong: It does not form ammonia.
C right: Direct reaction of SO3 with water forms a dangerous mist of sulfuric acid.
D wrong: SO3 is reactive with water.

29. A

A right: SO3 absorbed in concentrated sulfuric acid forms oleum.
B wrong: Ammonia is unrelated.
C wrong: Sulfur dioxide is a reactant earlier in the process.
D wrong: Hydrogen sulfide is not formed.

30. C

A wrong: Oleum is not diluted to make nitric acid.
B wrong: Hydrochloric acid is unrelated.
C right: Oleum is diluted carefully with water to produce sulfuric acid.
D wrong: Sulfurous acid is H2SO3, not the Contact process product.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

31. B

Forward reaction is endothermic and produces more gas moles.
Formation of PCl5 is the reverse reaction: exothermic and fewer gas moles.

A wrong: High temperature favours decomposition, not PCl5.
B right: Low temperature favours exothermic reverse reaction; high pressure favours fewer gas molecules, PCl5.
C wrong: Both conditions favour products PCl3 and Cl2.
D wrong: Low pressure favours more gas molecules, not PCl5.

32. C

Left side has 2 moles of gas.
Right side has 2 moles of gas.

A wrong: Equal gas moles means no shift left.
B wrong: Equal gas moles means no shift right.
C right: Pressure has no effect on equilibrium position.
D wrong: Iodine does not become catalyst.

33. A

Forward reaction is exothermic and gas moles decrease from 3 to 1.

A right: Low temperature favours exothermic forward reaction; high pressure favours fewer gas moles, methanol.
B wrong: Both conditions reduce yield.
C wrong: High pressure helps, but high temperature lowers yield.
D wrong: Low temperature helps, but low pressure lowers yield.

34. C

A wrong: Catalyst does not shift equilibrium to products.
B wrong: Catalyst does not shift equilibrium to reactants.
C right: Catalyst makes equilibrium reached faster but final equilibrium position is unchanged.
D wrong: Catalyst does not increase equilibrium yield.

35. B

A wrong: Concentrations do not have to be equal.
B right: Concentrations remain constant because forward and reverse rates are equal.
C wrong: Products do not have to be greater.
D wrong: Particles keep colliding and reacting.

36. B

Forward reaction is exothermic and forms colourless N2O4.

A wrong: Cooling favours N2O4, not brown NO2.
B right: Cooling shifts equilibrium to colourless N2O4, so brown colour becomes paler.
C wrong: Cooling does not shift to NO2.
D wrong: Equilibrium does not stop.

37. B

2NO2 has 2 gas moles; N2O4 has 1 gas mole.

A wrong: Increased pressure does not favour more gas moles.
B right: Increased pressure favours fewer gas moles, so more N2O4 forms.
C wrong: Gas moles are not equal.
D wrong: Both gases do not disappear.

38. B

Forward reaction is endothermic and increases gas moles from 1 to 2.

A wrong: Decreasing temperature favours reverse reaction and increasing pressure favours fewer gas moles.
B right: Increasing temperature favours endothermic forward reaction; decreasing pressure favours more gas moles, B.
C wrong: Low temperature favours reverse.
D wrong: High pressure favours reverse.

39. B

Forward reaction is exothermic and gas moles decrease from 3 to 2.
To favour reactants: favour endothermic reverse and more gas moles.

A wrong: Increasing pressure favours products; decreasing temperature favours products.
B right: Decreasing pressure favours reactants; increasing temperature favours reverse endothermic reaction.
C wrong: Increased pressure favours products.
D wrong: Decreased temperature favours products.

40. C

Gas moles are equal on both sides: 2 ⇌ 2.
Pressure does not affect position. Catalyst does not affect position. Temperature does.

A wrong: No shift because gas moles are equal.
B wrong: No shift because gas moles are equal.
C right: Temperature affects equilibrium because forward reaction is exothermic.
D wrong: Catalyst does not affect equilibrium position.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

41. C

A wrong: Reverse reaction is not zero at equilibrium.
B wrong: Reverse rate is not half.
C right: At equilibrium, forward rate equals reverse rate, so reverse rate is 15 mol/dm3/s.
D wrong: Reverse rate is not greater.

42. C

A wrong: Forward reaction continues.
B wrong: Reverse reaction continues.
C right: If mixture contains mostly reactants at equilibrium, equilibrium lies to the reactant side.
D wrong: It can still be reversible.

43. A

A right: Adding reactant immediately increases forward reaction rate because reactant concentration is higher.
B wrong: Reverse rate increases later as more product forms.
C wrong: Rates do not become zero.
D wrong: Equilibrium can be restored.

44. A

A right: Removing product shifts equilibrium right to make more product.
B wrong: It does not shift to make more reactant.
C wrong: Reactions do not stop.
D wrong: Catalyst is not destroyed.

45. B

A wrong: Increasing temperature increases rate but decreases ammonia yield because forward reaction is exothermic.
B right: Increasing pressure increases rate and shifts equilibrium towards fewer gas molecules, ammonia.
C wrong: Removing catalyst decreases rate.
D wrong: Decreasing pressure lowers yield and rate.

46. A

A right: Higher temperature increases rate but decreases ammonia yield because ammonia formation is exothermic.
B wrong: Decreasing temperature increases yield but lowers rate.
C wrong: Increasing pressure increases both rate and yield.
D wrong: Removing ammonia increases yield/production but is not about rate increase.

47. A

A right: Low temperature gives higher equilibrium yield but slow rate; high temperature gives faster rate but lower yield.
B wrong: Low temperature gives high yield, not low yield.
C wrong: Temperature affects both rate and yield.
D wrong: High temperature lowers yield for an exothermic reaction.

48. B

A wrong: Low pressure gives low yield.
B right: High pressure increases yield and rate but is expensive and dangerous, so a compromise pressure is used.
C wrong: Pressure affects both rate and yield.
D wrong: High pressure raises ammonia yield because products have fewer gas molecules.

49. A

A right: Lower temperature favours SO3 because forward reaction is exothermic, but rate becomes too slow.
B wrong: Higher temperature lowers SO3 yield.
C wrong: Catalyst does not increase equilibrium yield.
D wrong: Higher pressure, not low pressure, favours SO3.

50. A

A right: Haber process makes ammonia; Contact process makes sulfuric acid.
B wrong: Haber uses iron; Contact uses V2O5.
C wrong: Both key forward reactions are exothermic.
D wrong: Higher pressure favours products in both because products have fewer gas molecules.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.