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Chemistry CIE iGCSE:
Reversible Reactions
+ Equilibrium

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Triple only! Not for double science.

1. When methane reacts with steam the temperature falls.

The equation for the reaction is:

CH4 + H2OCO + 3H2

What does the symbol represent, and is the reaction between methane and steam exothermic or endothermic?

 
  meaning of Reaction type
A equilibrium endothermic
B equilibrium exothermic
C Reversible reaction endothermic
D Reversible reaction exothermic

Q2-3:
Hydrated copper(II)sulfate can be converted to anhydrous copper(II)sulfate by heating strongly. The reaction is reversible:

CuSO4.5H2O(s)CuSO4(s)  +  5H2O(g)

The forward reaction is endothermic and absorbs 78.2 kJ/mol.

 
2. Which statement is true about the reverse reaction?
  • A.   It is exothermic and releases less than 78.2kJ/mol
  • B.   It is exothermic and releases 78.2kJ/mol
  • C.   It is also endothermic and absorbs more than 78.2kJ/mol
  • D.   It is also endothermic and absorbs 78.2kJ/mol
3. How could the student make the reaction go in the reverse direction?
  • A.   cool some anhydrous copper(II)sulfate in an ice bath
  • B.   cool some hydrated copper(II)sulfate in an ice bath
  • C.   add water to anhydrous copper(II)sulfate
  • D.   add water to hydrated copper(II)sulfate
4. Which one of the following statements is true about reversible reactions?
  • A. All reactions are reversible under lab conditions
  • B. All reversible reactions are in dynamic equilibrium
  • C. All reactions go to completion under lab conditions
  • D. The direction of some reversible reactions can be altered by changing the reaction conditions

Q5+6:
Reversible reactions that are in dynamic equilibrium have two characteristics.

 
5. One of the characteristics is that the ..
  • A.   forward reaction is faster than the reverse reaction
  • B.   forward reaction is slower than the reverse reaction
  • C.   forward and reverse reactions both stop
  • D.   forward and reverse reactions occur at the same rate
6. The second characteristic is that the ..
  • A.   concentrations of reactants and products are equal
  • B.   concentrations of reactants and products are constant
  • C.   concentration of reactants is less than concentration of products
  • D.   concentration of reactants is more than concentration of products
7. Which words best fill the gaps in the following sentences?

An increase in temperature shifts the position of equilibrium in the direction of the …….(1)…… reaction.

A decrease of pressure shifts the position of equilibrium in the direction that produces ……(2)……. moles of gas

 

  Gap (1) Gap (2)
A exothermic more
B exothermic less
C endothermic more
D endothermic less

Q8-9:
The following reaction is used in industry during the production of sulfuric acid.
The forward reaction is exothermic.

2SO2(g)  +  O2(g)2SO3(g)     

What will happen to the amount of product, SO3, formed at equilibrium if the following changes are made to the reaction conditions? 

  

8. If the pressure is increased, the amount of product .
9. If the temperature is increased, the amount of product .

Q10-11:
The following reaction between carbon monoxide and hydrogen is exothermic.

CO(g)  +  2H2(g)CH3OH(g)   

  

10. What happens to the rate of reaction and the position of equilibrium when the temperature is increased?

  Rate of Reaction Position of equilibrium
A increases Moves to the right
B increases Moves to the left
C decreases Moves to the right
D decreases Moves to the left

11. Which combination of temperature and pressure will give the greatest yield of methanol?

  Temperature Pressure
A high high
B high low
C low high
D low low