Topic 13: Chemical Equilibria

Be able to deduce an expression for Kc , for homogeneous and heterogeneous systems, in terms of equilibrium concentrations.

Use —deduce an expression for kc , for homogeneous and heterogeneous systems, in terms of equilibrium concentrations to connect the rule to the data and decision in the question.

This matters because —deduce an expression for kc , for homogeneous and heterogeneous systems, in terms of equilibrium concentrations determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —deduce an expression for kc , for homogeneous and heterogeneous systems, in terms of equilibrium concentrations to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Deduce an expression for Kc , for homogeneous and heterogeneous systems, in terms of equilibrium concentrations is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to deduce an expression for Kp for homogeneous and heterogeneous systems, in terms of equilibrium partial pressures in atm.

Use —deduce an expression for kp for homogeneous and heterogeneous systems, in terms of equilibrium partial pressures in atm to connect the rule to the data and decision in the question.

This matters because —deduce an expression for kp for homogeneous and heterogeneous systems, in terms of equilibrium partial pressures in atm determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —deduce an expression for kp for homogeneous and heterogeneous systems, in terms of equilibrium partial pressures in atm to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Deduce an expression for Kp for homogeneous and heterogeneous systems, in terms of equilibrium partial pressures in atm is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate a value, with units where appropriate, for the equilibrium constants (Kc and Kp) for homogeneous and heterogeneous reactions, from experimental data.

Use —a value, with units where appropriate, for the equilibrium constants (kc and kp) for homogeneous and heterogeneous to connect the rule to the data and decision in the question.

This matters because —a value, with units where appropriate, for the equilibrium constants (kc and kp) for homogeneous and heterogeneous determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —a value, with units where appropriate, for the equilibrium constants (kc and kp) for homogeneous and heterogeneous to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —A value, with units where appropriate, for the equilibrium constants (Kc and Kp) for homogeneous and heterogeneous is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand how, if at all, a change in temperature, pressure or the presence of a catalyst affects the equilibrium composition in a homogeneous or heterogeneous system.

Use —how, if at all, a change in temperature, pressure or the presence of a catalyst affects the equilibrium composition in to connect the rule to the data and decision in the question.

This matters because —how, if at all, a change in temperature, pressure or the presence of a catalyst affects the equilibrium composition in determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —how, if at all, a change in temperature, pressure or the presence of a catalyst affects the equilibrium composition in to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —How, if at all, a change in temperature, pressure or the presence of a catalyst affects the equilibrium composition in is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand that the value of the equilibrium constant is not affected by changes in concentration or pressure or by the addition of a catalyst.

Use —the value of the equilibrium constant is not affected by changes in concentration or pressure or by the addition of to connect the rule to the data and decision in the question.

This matters because —the value of the equilibrium constant is not affected by changes in concentration or pressure or by the addition of determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the value of the equilibrium constant is not affected by changes in concentration or pressure or by the addition of to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The value of the equilibrium constant is not affected by changes in concentration or pressure or by the addition of is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Know the effect of changing the temperature on the equilibrium constant (Kc and Kp) for both exothermic and endothermic reactions.

Use —the effect of changing the temperature on the equilibrium constant (kc and kp) for both exothermic and endothermic reactions to connect the rule to the data and decision in the question.

This matters because —the effect of changing the temperature on the equilibrium constant (kc and kp) for both exothermic and endothermic reactions determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the effect of changing the temperature on the equilibrium constant (kc and kp) for both exothermic and endothermic reactions to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The effect of changing the temperature on the equilibrium constant (Kc and Kp) for both exothermic and endothermic reactions is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand that the effect of temperature on the position of equilibrium is explained using a change in the value of the equilibrium constant.

Use —the effect of temperature on the position of equilibrium is explained using a change in the value of the equilibrium to connect the rule to the data and decision in the question.

This matters because —the effect of temperature on the position of equilibrium is explained using a change in the value of the equilibrium determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the effect of temperature on the position of equilibrium is explained using a change in the value of the equilibrium to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The effect of temperature on the position of equilibrium is explained using a change in the value of the equilibrium is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand the effect of a change in temperature on: i the value of ∆Stotal ii the magnitude of the equilibrium constant, since ∆Stotal = R lnK.

Use —the effect of a change in temperature on: i the value of ∆stotal ii the magnitude of the equilibrium constant, since ∆stotal to connect the rule to the data and decision in the question.

This matters because —the effect of a change in temperature on: i the value of ∆stotal ii the magnitude of the equilibrium constant, since ∆stotal determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the effect of a change in temperature on: i the value of ∆stotal ii the magnitude of the equilibrium constant, since ∆stotal to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The effect of a change in temperature on: i the value of ∆Stotal ii the magnitude of the equilibrium constant, since ∆Stotal is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to apply knowledge of the value of equilibrium constants to predict the extent to which a reaction takes place.

Use —apply knowledge of the value of equilibrium constants to predict the extent to which a reaction takes place to connect the rule to the data and decision in the question.

This matters because —apply knowledge of the value of equilibrium constants to predict the extent to which a reaction takes place determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —apply knowledge of the value of equilibrium constants to predict the extent to which a reaction takes place to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Apply knowledge of the value of equilibrium constants to predict the extent to which a reaction takes place is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.