Chemical Reaction IGCSE

What does Le Chatelier's Principle state?

• Le Chatelier's Principle only applies to chemical reactions in a laboratory setting

• A system at equilibrium will not respond to any external changes

• If a system at equilibrium is disturbed, it will shift to counteract the disturbance and establish a new equilibrium.

• The equilibrium position of a system cannot be altered

Define oxidation and reduction reactions.

• Oxidation is the gain of protons, reduction is the loss of protons.

• Oxidation is the gain of electrons, reduction is the loss of electrons.

• Oxidation is the loss of electrons, reduction is the gain of electrons.

• Oxidation is the gain of energy, reduction is the loss of energy.

How does temperature affect the rate of a reversible reaction?

• Temperature always decreases the rate of a reversible reaction.

• Decreasing temperature generally increases the rate of a reversible reaction.

• Increasing temperature generally increases the rate of a reversible reaction.

• Temperature has no effect on the rate of a reversible reaction.

What happens to the equilibrium constant when the concentration of reactants is increased?

• Remains the same

• Decreases

• Becomes negative

• Increases exponentially

In a redox reaction, which element is oxidized and which is reduced?

• The element that is reduced loses electrons, and the element that is oxidized gains electrons.

• The element that is oxidized loses electrons, and the element that is reduced gains electrons.

• The element that is reduced is the one that gains electrons.

• The element that is oxidized gains electrons, and the element that is reduced loses electrons.

What is the role of a catalyst in a reversible reaction?

• A catalyst slows down the attainment of equilibrium by increasing the activation energy for both the forward and reverse reactions.

• A catalyst only affects the forward reaction in a reversible reaction.

• A catalyst changes the equilibrium constant of a reversible reaction.

• A catalyst speeds up the attainment of equilibrium by lowering the activation energy for both the forward and reverse reactions.

How does pressure impact the equilibrium position in a reversible reaction?

• Pressure causes the reaction to stop completely.

• The equilibrium position shifts towards the side with fewer gas molecules.

• Pressure has no effect on the equilibrium position.

• The equilibrium position shifts towards the side with more gas molecules.

Write the half-reaction for the oxidation of iron (Fe) to Fe^3+.

• Fe -> Fe^5+ + 5e^-

• Fe -> Fe^4+ + 4e^-

• Fe -> Fe^3+ + 3e^-

• Fe -> Fe^2+ + 2e^-

Describe the process of dynamic equilibrium in a reversible reaction.

• Dynamic equilibrium leads to a sudden change in temperature

• Dynamic equilibrium results in the complete consumption of reactants

• Dynamic equilibrium in a reversible reaction occurs when the rates of the forward and reverse reactions are equal, leading to a constant concentration of reactants and products.

• Dynamic equilibrium only occurs in irreversible reactions

What is the relationship between the rate of the forward and reverse reactions at equilibrium?

• Rate of forward reaction > Rate of reverse reaction

• Rate of forward reaction < Rate of reverse reaction

• Rate of forward reaction is not related to Rate of reverse reaction

• Rate of forward reaction = Rate of reverse reaction