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Equilibrium (paper 1 style questions)

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International baccalaureate Chemistry (Equilibrium) Quiz on Equilibrium (paper 1 style questions), created by Emine Afiyet Fra on 15/09/2013.
Emine Afiyet Fra
Quiz by Emine Afiyet Fra, updated more than 1 year ago
Emine Afiyet Fra
Created by Emine Afiyet Fra over 10 years ago
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Resource summary

Question 1

Question
Which statement is true about chemical reactions at equilibrium?
Answer
  • The forward and backward reactions proceed at equal rates
  • The forward and backward reactions have stopped
  • The concentrations of the reactants and products are equal
  • The forward reaction is exothermic

Question 2

Question
Chemical equilibrium is referred to as dynamic because, at equilibrium, the...
Answer
  • equilibrium constant changes
  • reactants and products keep reacting
  • rates of the forward and backward reactions change
  • concentrations of the reactants and products continue to change

Question 3

Question
What is the equilibrium expression for the reaction: N2 + 3H2 --> 2NH3 (all in the gaseous state)?
Answer
  • [NH3]^2/[N2][H2]^3
  • 2[NH3]/3[N2][H2]
  • [NH3]/[N2][H2]
  • 2[NH3]/[N2][H2]

Question 4

Question
For a reaction which goes to completion, the equilibrium constant, Kc, is:
Answer
  • more than 1 (Kc >>1)
  • less than 1 (Kc
  • = 1
  • = 0

Question 5

Question
The equilibrium constant for the reaction below is 1.0 x 10^-14 at 25oC and 2.1 x 10^-14 at 35oC. What can be concluded from this information? 2H2O (l) H3O+ (aq) + OH- (aq)
Answer
  • The ionization of water is endothermic
  • [H3O+] decreases as the temperature is raised
  • Water is a stronger electrolyte at 25oC
  • [H3O+] is greater than [OH+] at 35oC

Question 6

Question
Ethanol is manufactured from ethene using the reaction: C2H4 + H2O C2H5OH (Delta-H = -46 KJ) Which conditions favour the highest yield of ethanol?
Answer
  • High pressure and low temperature
  • High pressure and high temperature
  • Low pressure and low temperature
  • Low pressure and high temperature

Question 7

Question
N2O4 and NO2 produce an equilibrium mixture according to the equation: N2O4 2NO2 (Delta-H = 57.2 KJ/mol) An increase in the equilibrium concentration of NO2 can be produced by increasing which of the factors below? 1) Pressure 2) Temperature
Answer
  • 1 only
  • 2 only
  • both 1 and 2
  • neither 1 or 2

Question 8

Question
Which changes will increase the amount of SO3 (g) at equilibrium? 2SO2 + O2 2SO3 (Delta-H = -197KJ) 1) increasing temperature 2) decreasing volume 3) adding a catalyst
Answer
  • 1 only
  • 2 only
  • 1 and 3 only
  • 1, 2 and 3

Question 9

Question
For the reaction N2 + 3H2 2NH3 (Delta-H = -92 KJ) What conditions will produce the highest percentage of NH3 at equilibrium?
Answer
  • High pressure and high temperature
  • High pressure and low temperature
  • Low pressure and high temperature
  • Low pressure and low temperature

Question 10

Question
Hydrogen and iodine react in a closed vessel to form hydrogen iodide. H2 + I2 2HI at 350oC, Kc = 60 at 445oC, Kc = 47
Answer
  • Increased temperature as the forward reaction is exothermic, and increased pressure as there are two gaseous reactants and only one gaseous product
  • Increased temperature as the forward reaction is endothermic, and pressure has no effect as there are equal amounts, in mol, of gaseous reactants and products
  • Decreased temperature as the forward reaction is exothermic, and decreased pressure as there are 2 moles of gaseous product but only 1 mole of each gaseous reactant
  • Decreased temperature as the forward reaction is exothermic, and pressure has no effect as there are equal amounts, in mol, of gaseous reactants and products

Question 11

Question
An increase in temperature increases the amount of chlorine present in the following equilibrium. PCL5 (s) PCL3 (l) + CL2 (g) What is the best explanation for this?
Answer
  • The higher temperature increases the rate of the forward reaction only.
  • The higher temperature increases the rate of the reverse reaction only
  • The higher temperature increases the rate of both reactions but the reverse reaction is affected more than the forward
  • The higher temperature increases the rate of both reactions but the forward reaction is affected more than the reverse

Question 12

Question
The reaction between sulfur dioxide and oxygen (the contact process) occurs according to the equation below: 2SO2 + O2 2SO3 (Delta-H = -197) A higher equilibrium concentration of SO3 will be produced by all of the following changes in a reaction conditions except...
Answer
  • increasing pressure
  • adding more O2
  • adding a catalyst
  • decreasing the temperature

Question 13

Question
The reaction between methane and hydrogen sulfide is represented by the equation below: CH4 + 2H2S CS2 + 4H2 What is the equilibrium expression for this reaction?
Answer
  • [CS2][H2]/[CH4][H2S]
  • 4[CS2][H2]/2[CH4][H2S]
  • [CS2] 4[H2]/[CH4] + 2[H2S]
  • [CS2][H2]^4/[CH4][H2S]^2

Question 14

Question
At 35oC, Kc = 1.6 x 10^-5 mol/dm^3 for the reaction: 2NOCL 2NO + Cl2 Which relationship must be correct at equilibrium?
Answer
  • [NO] = [NOCl]
  • 2[NO] = [Cl2]
  • [NOCl]
  • [NO]
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