Day 20 pH of Acids and Bases classwork

A tenfold increase in hydronium ion concentration is represented by

• a decrease of one unit of pH

• a decrease of 10 units of pH

• an increase of one unit of pH

• an increase of 10 units of pH

Answer explanation

A tenfold increase in hydronium ion concentration results in a decrease of one unit of pH, as pH is the negative logarithm of the hydronium ion concentration.

The acidity or alkalinity of a solution can be measured by its

• pH value

• electronegativity value

• boiling point

• freezing point

Answer explanation

The acidity or alkalinity of a solution can be measured by its pH value, making it the correct choice among the options provided.

Solution A has a pH value of 2.0 and solution B has a pH value of 4.0. How many times greater is the hydronium ion concentration in solution A than the hydronium ion concentration in solution B?

• 10

• 2

• 100

• 4

Answer explanation

The hydronium ion concentration is determined by the pH value using the formula [H+] = 10^(-pH). So, the concentration in solution A is 100 times greater than in solution B (10^(-2) / 10^(-4) = 100).

The table below shows the molar concentrations of hydronium ion, H₃O⁺, in four different solutions. Which solution has the highest pH?

• A

• B

• C

• D

Answer explanation

Solution D has the highest pH as it has the lowest molar concentration of hydronium ion, H₃O⁺, which is inversely related to pH.

Compared to a 1.0-liter aqueous solution with a pH of 7.0, a 1.0-liter aqueous solution with a pH of 5.0 contains

• 10 times more hydronium ions

• 100 times more hydronium ions

• 10 times more hydroxide ions

• 100 times more hydroxide ions

Answer explanation

A solution with a pH difference of 2 corresponds to a 100-fold difference in hydronium ion concentration. Therefore, a solution with a pH of 5.0 has 100 times more hydronium ions than a solution with a pH of 7.0.

When the concentration of hydrogen ions in a solution is decreased by a factor of ten, the pH of the solution

• increases by 1

• increases by 10

• decreases by 1

• decreases by 10

Answer explanation

When the concentration of hydrogen ions decreases by a factor of ten, the pH increases by 1 according to the logarithmic nature of the pH scale.

Compared to a solution with a pH value of 7, a solution with a thousand times greater hydronium ion concentration has a pH value of

• 10

• 7

• 3

• 4

Answer explanation

A solution with a thousand times greater hydronium ion concentration than pH 7 has a pH value of 3, as each unit change in pH represents a 10-fold difference in hydronium ion concentration.

Which change in the H⁺ ion concentration of an aqueous solution represents a decrease of one unit on the pH scale?

• a tenfold increase

• a tenfold decrease

• a hundredfold increase

• a hundredfold decrease

Answer explanation

A decrease of one unit on the pH scale corresponds to a tenfold decrease in the H⁺ ion concentration of an aqueous solution.

Which statement describes characteristics of a 0.01 M KOH(aq) solution?

When the hydronium ion concentration of an aqueous solution is increased by a factor of 10, the pH value of the solution

• decreases by 1

• increases by 1

• decreases by 10

• increases by 10