How Far? The Extent of Chemical Change (DP IB Chemistry)

False.

In dynamic equilibrium, the concentrations of reactants and products are constant, not necessarily equal.

True.

Equilibrium can be reached in open flasks for reactions taking place entirely in solution.

False.

Dynamic equilibrium can be approached starting with either reactants or products.

For reactions involving gases, equilibrium can only be reached in a closed system, not in an open system.

The equilibrium constant expression is an equation that links the equilibrium constant, K, to the concentrations of reactants and products at equilibrium, taking into account the stoichiometry of the equation.

The general form of the equilibrium constant expression is:

K = [C]^c [D]^d / [A]^a [B]^b

False.

Solids are ignored in equilibrium constant expressions.

The square brackets represent the equilibrium concentrations of the substances in mol dm^-3.

True.

The equilibrium constant, K, is specific to a given equation.

When a reaction equation is reversed, the equilibrium constant becomes the reciprocal of the original K value.

False.

The equilibrium constant expression uses equilibrium concentrations of reactants and products.

Concentrations in equilibrium constant expressions are typically expressed in mol dm^-3.

False.

The equilibrium constant expression excludes solids and pure liquids.

The size of the equilibrium constant, K, indicates how the equilibrium mixture is made up with respect to reactants and products.

False.

When K > 1, the equilibrium lies to the right hand side (products are favored).

When K >> 1, the equilibrium lies far over to the right hand side and the reaction almost goes to completion.

False.

When K < 1, the concentration of reactants is greater than the concentration of products.

When K = 1, there are significant amounts of both reactants and products, and equilibrium does not lie in favor of either.

No, K is constant at a specified temperature but can change with temperature.

True.

Stronger acids always have a higher value of K than weaker acids.

K' = 1/K or K' = K^-1, where K' is the equilibrium constant for the reverse reaction.

False.

The equilibrium constant, K, is not affected by changes in concentration of reactants or products at a given temperature.

Le Chatelier's principle states that if a change is made to a system at dynamic equilibrium, the position of the equilibrium moves to minimise this change.

False.

Increasing the concentration of a reactant shifts the equilibrium to the right.

Decreasing the concentration of a product shifts the equilibrium to the right to reduce the effect of the decrease.

An increase in pressure shifts the equilibrium in the direction that produces the smaller number of gas molecules.

False.

Changes in pressure only affect reactions where the reactants or products are gases, and the number of moles of gaseous reactant are different to the number of moles of gaseous product.

An increase in temperature shifts the equilibrium in the endothermic direction, favoring the products for an endothermic reaction.

True.

Catalysts have no effect on the position of equilibrium or the value of K.

Catalysts only cause a reaction to reach its equilibrium faster, without affecting the position of equilibrium.

Le Chatelier's principle can be applied to heterogeneous equilibria in the same way as homogeneous equilibria, considering the effects of changes in concentration, pressure, and temperature.

True.

If the forward reaction is exothermic, the backward reaction is favoured by increasing the temperature.

Increasing the pressure would favour the forward reaction.

This is because there are 4 molecules on the left and side and 2 molecules on the right hand side.

An increase in pressure will favour the side with the fewest number of molecules.

If the forward reaction is endothermic, a high temperature would increase the yield of products.

This is because the forward reaction is endothermic. A high temperature would favour the endothermic pathway to oppose the increase.

False.

A catalyst speeds up the rate of both the forward and backward reactions.

False.

Increasing pressure shifts the equilibrium to favour the side with fewer gas molecules.

Equilibrium shifts to the left to reduce the effect of a decrease in reactant (or an increase in the concentration of product).

Equilibrium shifts in the direction that produces the larger number of molecules of gas to increase the pressure again.

The reaction quotient, Q, is calculated using the same equation as the equilibrium constant expression, but with non-equilibrium concentrations of reactants and products.

False.

The expression for Q is the same as K, but uses non-equilibrium concentrations.

When Q = K, the reaction is at equilibrium.

If Q < K, the reaction will proceed to the right in favor of the products.

False.

If Q > K, the reaction will proceed to the left in favor of the reactants.

By calculating Q using concentration values and comparing it to K, we can determine if a reaction is at equilibrium (Q = K) or not (Q ≠ K).

False.

Q is not a fixed value and can be measured at any time, unlike K which is constant at a given temperature.

Q provides information about how far a reaction is from equilibrium and in which direction the reaction will proceed to reach equilibrium.

True.

Q can be calculated using initial concentrations of reactants and products, or concentrations at any point during the reaction.

As a reaction progresses towards equilibrium, Q approaches the value of K.

False.

Sometimes amounts in moles are given, and concentrations need to be calculated using the volume of the reaction mixture.

Concentration (mol dm^-3) = amount of substance (mol) / volume (dm³)

When K < 10^-3, the initial concentration of reactants can be approximated as the equilibrium concentration of reactants.

The assumption is that the change from the initial amount of reactant to the equilibrium amount is close to zero when K is very small.

False.

The approximation method is only valid when K < 10^-3.

The equilibrium constant for the reaction is:

The value of K is:

• K =

• K = = 0.625

CH₃COOH (I) + C₂H₅OH (I) ⇌ CH₃COOC₂H₅ (I) + H₂O (I)

If the concentration of ethyl ethanoate increases by 0.25 mol dm^-3, the concentration of ethanoic acid decreases by 0.25 mol dm^-3.

False.

2X (I) + Y (I) ⇌ 2Z (I)

If the concentration of Z increases by 0.5 mol dm^-3, the concentration of Y decreases by 0.25 mol dm^-3.

The concentration of ethanol, in mol dm^-3 is:

• Concentration = moles / volume in dm³

• Concentration = 0.15 / 0.25 = 0.6 mol dm^-3

The equation relating Gibbs energy change to the equilibrium constant is:

ΔG° = -RT ln K

True.

A negative ΔG° always indicates that K > 1, meaning the products are favored at equilibrium.

When ΔG° = 0, the equilibrium constant K = 1, meaning neither reactants nor products are favored at equilibrium.

False.

The equilibrium constant is independent of reaction kinetics and provides no information about individual rates of reaction.

A negative ΔG° indicates that a reaction is feasible (spontaneous) under standard conditions.

A negative ΔG° indicates that the equilibrium concentration of products is greater than the equilibrium concentration of reactants.

False.

As ΔG° becomes more negative, the value of the equilibrium constant increases.

ΔG° is typically expressed in kJ mol^-1 in the equation ΔG° = -RT ln K.

The rearrranged equation is:

True.

The relationship between ΔG° and K is temperature-dependent, as shown by the presence of T in the equation ΔG° = -RT ln K.