Acids, Bases, and Reactions Quiz

The pH scale measures the concentration of:

• Oxygen ions

• Hydrogen ions

• Hydroxide molecules

• Electrons

Answer explanation

The pH scale measures the concentration of hydrogen ions (H+). A lower pH indicates a higher concentration of hydrogen ions, making a solution more acidic.

A solution with a pH of 1 is:

• Neutral

• Weakly acidic

• Strongly acidic

• Strongly alkaline

Answer explanation

A solution with a pH of 1 is strongly acidic, as the pH scale ranges from 0 to 14, where values below 7 indicate acidity. Therefore, the correct choice is 'Strongly acidic'.

A solution with a pH of 8 is described as:

• Neutral

• Weakly alkaline

• Weakly acidic

• Strongly acidic

Answer explanation

A solution with a pH of 8 is above the neutral pH of 7, indicating it is weakly alkaline. Solutions with pH values below 7 are acidic, while those above 7 are alkaline.

What is the pH of a neutral solution?

• 1

• 7

• 10

• 14

Answer explanation

A neutral solution has a pH of 7, which indicates a balance between hydrogen ions (H+) and hydroxide ions (OH-). Values below 7 are acidic, while values above 7 are basic.

The higher the concentration of hydrogen ions in a solution:

• The higher the pH

• The lower the pH

• The pH stays the same

• The solution becomes more alkaline

Answer explanation

The concentration of hydrogen ions is inversely related to pH. As hydrogen ion concentration increases, pH decreases, making the solution more acidic. Therefore, the correct answer is 'The lower the pH'.

Which indicator changes colour depending on pH value?

• Benedict’s solution

• universal indicator

• Biuret reagent

• Iodine

Answer explanation

The universal indicator changes color across a wide range of pH values, providing a visual representation of acidity or alkalinity. In contrast, Benedict’s solution, Biuret reagent, and iodine do not indicate pH changes.

Universal indicator shows a green colour at pH:

• 2

• 5

• 7

• 9

Answer explanation

Universal indicator shows green at pH 7, which is neutral. Values below 7 indicate acidity (red to yellow), while values above 7 indicate alkalinity (blue to purple). Therefore, the correct answer is 7.

Strong alkalis have a pH of:

• 1–3

• 4–6

• 7

• 12–14

Answer explanation

Strong alkalis, such as sodium hydroxide, have a pH range of 12 to 14, indicating they are highly basic. This is significantly higher than neutral pH (7) and much higher than acidic ranges (1-6).

What is the formula for hydrochloric acid?

• HCl

• H₂SO₄

• HNO₃

• CH₃COOH

Answer explanation

The formula for hydrochloric acid is HCl, which consists of one hydrogen atom and one chlorine atom. The other options represent different acids: H₂SO₄ is sulfuric acid, HNO₃ is nitric acid, and CH₃COOH is acetic acid.

What is the formula for sulfuric acid?

• HCl

• H₂SO₄

• HNO₃

• H₂CO₃

Answer explanation

The formula for sulfuric acid is H₂SO₄, which consists of two hydrogen (H) atoms, one sulfur (S) atom, and four oxygen (O) atoms. The other options represent different acids: HCl is hydrochloric acid, HNO₃ is nitric acid, and H₂CO₃ is carbonic acid.