pH and Weak Acid/Base Calculations

The video tutorial explains how to calculate the pH of weak acid and base solutions. It covers the importance of knowing weak acids and bases, how to compare their strengths using KA, pKa, KB, and pKB, and provides step-by-step instructions for calculating pH. The tutorial also discusses assumptions made during calculations to simplify the process and ensure accuracy.

Why is it important to memorize the list of common weak acids?

• Because they are stronger than strong acids.

• Because they are the only acids that exist.

• Because the calculations for weak and strong acids differ.

• Because they are used in all chemical reactions.

What happens to the strength of a weak acid as its KA value increases?

• The acid becomes weaker.

• The acid becomes neutral.

• The acid strength remains unchanged.

• The acid becomes stronger.

How is the pKa value related to the strength of an acid?

• pKa has no relation to acid strength.

• As pKa decreases, acid strength increases.

• pKa is only used for bases.

• As pKa increases, acid strength increases.

What is the first step in calculating the pH of a weak acid solution?

• Calculate the molarity of water.

• Set up the KA equilibrium expression.

• Determine the concentration of the base.

• Find the pOH of the solution.

Why do chemists often avoid using the quadratic equation in pH calculations?

• It is not accurate for pH calculations.

• It is too complex for weak acids.

• It is time-consuming and can be simplified.

• It is only used for strong acids.

What assumption is made to simplify the pH calculation of a weak acid?

• The acid completely dissociates.

• The base concentration is higher than the acid.

• The concentration of hydronium is zero.

• The value of X is small compared to the initial concentration.

How do you verify the assumption that X is small in pH calculations?

• By checking if X is greater than the initial concentration.

• By dividing X by the initial concentration and multiplying by 100.

• By comparing X to the concentration of water.

• By calculating the pOH of the solution.

What is the relationship between pH and pOH in a solution?

• pH plus pOH equals 14.

• pH plus pOH equals 7.

• pH minus pOH equals 14.

• pH and pOH are always equal.

What is the first step in calculating the pH of a weak base solution?

• Find the pH directly from the concentration.

• Determine the pKa of the base.

• Set up the KB equilibrium expression.

• Calculate the concentration of hydronium.

How is the concentration of hydroxide used to find the pH of a weak base?

• By calculating the pKa from the hydroxide concentration.

• By assuming it is equal to the pH.

• By directly converting it to pH.

• By using the concentration to find the pOH and then the pH.