Common Ion Effect and Equilibrium Concepts

The video tutorial explains the common ion effect, where a solution already containing an ion is mixed with an acid or base that shares the same ion. This affects the initial concentration in the ICE table, as the solution is not pure water. An example problem involving formic acid and sodium formate is used to illustrate the concept, showing how the presence of a common ion shifts equilibrium and affects pH. The tutorial also covers the mathematical approach to solving such problems, including the use of approximations when calculating equilibrium concentrations.

What is a common ion effect?

• The effect of adding a new ion to a solution.

• The effect observed when a solution already contains an ion that is also added by an acid or base.

• The effect of removing an ion from a solution.

• The effect of adding a common ion to pure water.

Why can't we assume zero initial concentration for the common ion in the ICE table?

• Because the ion does not affect the reaction.

• Because the ion is added later.

• Because the ion is already present in the solution.

• Because the ion is not present initially.

Why is it important to consider the initial concentration of ions in a solution?

• To measure the temperature change.

• To accurately calculate the equilibrium concentrations.

• To determine the solubility.

• To predict the color change.

What happens to sodium formate in the solution?

• It remains undissolved.

• It partially dissociates.

• It completely dissociates into sodium and formate ions.

• It reacts with water to form a new compound.

What is the role of sodium in the sodium formate solution?

• It reacts with formic acid.

• It changes the color of the solution.

• It is a spectator ion and does not affect pH.

• It acts as a catalyst.

How does the presence of a common ion affect the equilibrium of a reaction?

• It shifts the equilibrium to the left.

• It stops the reaction completely.

• It has no effect on the equilibrium.

• It shifts the equilibrium to the right.

What is the predicted effect on pH when a common ion is present?

• The pH remains the same.

• The pH decreases.

• The pH increases.

• The pH becomes neutral.

What does Le Chatelier's principle predict about a system at equilibrium?

• The system will speed up the reaction.

• The system will remain unchanged.

• The system will stop reacting.

• The system will shift to counteract any change.

What is the significance of negligible x in the equilibrium expression?

• It complicates the calculation.

• It simplifies the calculation by assuming x is zero.

• It changes the equilibrium constant.

• It has no significance.

How do you calculate the pH from hydronium ion concentration?

• By taking the negative log of the concentration.

• By dividing the concentration by 2.

• By multiplying the concentration by 10.

• By adding the concentration to 7.