Emine Afiyet Fra
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International baccalaureate (Equilibrium) Chemistry Test sobre Equilibrium (paper 1 style questions), creado por Emine Afiyet Fra el 15/09/2013.

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Emine Afiyet Fra
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Equilibrium (paper 1 style questions)

Pregunta 1 de 14

1

Which statement is true about chemical reactions at equilibrium?

Selecciona una o más de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 2 de 14

1

Chemical equilibrium is referred to as dynamic because, at equilibrium, the...

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 3 de 14

1

What is the equilibrium expression for the reaction: N2 + 3H2 --> 2NH3 (all in the gaseous state)?

Selecciona una de las siguientes respuestas posibles:

  • [NH3]^2/[N2][H2]^3

  • 2[NH3]/3[N2][H2]

  • [NH3]/[N2][H2]

  • 2[NH3]/[N2][H2]

Explicación

Pregunta 4 de 14

1

For a reaction which goes to completion, the equilibrium constant, Kc, is:

Selecciona una de las siguientes respuestas posibles:

  • more than 1 (Kc >>1)

  • less than 1 (Kc

  • = 1

  • = 0

Explicación

Pregunta 5 de 14

1

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)

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 6 de 14

1

Ethanol is manufactured from ethene using the reaction:
C2H4 + H2O C2H5OH (Delta-H = -46 KJ)
Which conditions favour the highest yield of ethanol?

Selecciona una de las siguientes respuestas posibles:

  • High pressure and low temperature

  • High pressure and high temperature

  • Low pressure and low temperature

  • Low pressure and high temperature

Explicación

Pregunta 7 de 14

1

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

Selecciona una de las siguientes respuestas posibles:

  • 1 only

  • 2 only

  • both 1 and 2

  • neither 1 or 2

Explicación

Pregunta 8 de 14

1

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

Selecciona una de las siguientes respuestas posibles:

  • 1 only

  • 2 only

  • 1 and 3 only

  • 1, 2 and 3

Explicación

Pregunta 9 de 14

1

For the reaction N2 + 3H2 2NH3 (Delta-H = -92 KJ)
What conditions will produce the highest percentage of NH3 at equilibrium?

Selecciona una de las siguientes respuestas posibles:

  • High pressure and high temperature

  • High pressure and low temperature

  • Low pressure and high temperature

  • Low pressure and low temperature

Explicación

Pregunta 10 de 14

1

Hydrogen and iodine react in a closed vessel to form hydrogen iodide.
H2 + I2 2HI
at 350oC, Kc = 60
at 445oC, Kc = 47

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 11 de 14

1

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?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 12 de 14

1

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...

Selecciona una de las siguientes respuestas posibles:

  • increasing pressure

  • adding more O2

  • adding a catalyst

  • decreasing the temperature

Explicación

Pregunta 13 de 14

1

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?

Selecciona una de las siguientes respuestas posibles:

  • [CS2][H2]/[CH4][H2S]

  • 4[CS2][H2]/2[CH4][H2S]

  • [CS2] 4[H2]/[CH4] + 2[H2S]

  • [CS2][H2]^4/[CH4][H2S]^2

Explicación

Pregunta 14 de 14

1

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

Selecciona una de las siguientes respuestas posibles:

  • [NO] = [NOCl]

  • 2[NO] = [Cl2]

  • [NOCl]

  • [NO]

Explicación

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