Questions on Equilibrium ocr

Q) Seawater is only slightly allkaline. This is due to the presence of HCO3- ions in the water.

HCO3-(aq) + H+ (aq) <==> CO2 (aq) + H2O (l)

Use this equation and Le Chatelier's principle to explain what would happen to the concentration of HCO3- ions in the seawater if more carbon dioxide were to dissolve in the water.

a) The position of equilibrium moves to the left, and the concentration of HCO3- ions would increases.

Q) Explain what is meant by the term dynamic equilibrium.

a) A chemical equilibrium between the forwards and reverse reaction where the rates of reaction are equal in a closed system, and the concentration of reactants and products remain the same.

Q) C6H5CH2CH3 (g) <==> C6H5CHCH2 + H2 (g) H'=117kJmol-1

Describe and explain the effect of the following changes on the yield of phenylethene produced in the equilibirium represented by the equation.

i) Carrying out the reaction at a higher temperature.

The yield of phenylethene increases, as the position of equilibrium moves in the endothermic direction.

ii) Carrying out the reaction at a higher pressure.

The yield of phenylethene decreases as the position of equilibrium moves to the side with fewer molecules.

Q) It is possible to stop the spread of disease like cholera by treating water with chlorine. The chlorine forms chloric (I) acid, HClO and hydrochloric acid HCl when it reacts with water.

Write the reversible equation for this reversible reaction of chlorine with water.

a) Cl2 + H2O <==> HClO + HCl

Q) Methanol can be made from carbon monoxide and hydrogen.

CO (g) + 2H2 (g) <==> CH3OH (g) H'= -91kJmol-1

Explain what is meant by the term dynamic equilibrium.

a) A chemical equilibrium between the forwards and reverse reaction whereby the rates of reaction are equal in a closed system and the concentration of reactants and products remains the same.

Q) Describe and explain the effect of the following changes on yield of methanol produced in this reaction.

Carrying out the temperature at a higher temperature

a) The yield of methanol would decrease, as the postion of equilibrium moves to the direction of the endothermic reaction.

Q) Increasing the total pressure of the reaction system

a)The yield of methanol would increase, as the position of equilibrium moves to the side with fewer particles.