Acids and Bases Practice Test

What does the pH scale measure?

• The temperature of a substance

• The acidity or basicity of a substance

• The density of a substance

• The color of a substance

Answer explanation

The pH scale measures the acidity or basicity of a substance, indicating how acidic (low pH) or basic (high pH) it is. This is crucial in chemistry and biology for understanding reactions and properties of substances.

What is the pH of a neutral solution?

• Less than 7

• Greater than 7

• 7

• 0

Answer explanation

A neutral solution has a pH of exactly 7, which indicates a balance between hydrogen ions (H+) and hydroxide ions (OH-). Values less than 7 are acidic, and greater than 7 are basic.

In a basic solution, which ions are greater in number?

• H+ ions

• OH- ions

• Na+ ions

• Cl- ions

Answer explanation

In a basic solution, the concentration of OH- ions is greater than that of H+ ions. This is because a basic solution has a higher pH, indicating more hydroxide ions present compared to hydrogen ions.

What taste is typically associated with acids?

• Bitter

• Sweet

• Sour

• Salty

Answer explanation

Acids are typically associated with a sour taste, which is why foods like lemons and vinegar are described as sour. This distinguishes them from other tastes like sweet, salty, or bitter.

According to Arrhenius, what does an acid release in water?

• Hydroxide ions

• Hydrogen ions

• Sodium ions

• Chloride ions

Answer explanation

According to Arrhenius, an acid is defined as a substance that releases hydrogen ions (H+) when dissolved in water. Therefore, the correct answer is hydrogen ions.

What is a Brønsted-Lowry base defined as?

• A proton donor

• A proton acceptor

• A hydroxide donor

• A hydroxide acceptor

Answer explanation

A Brønsted-Lowry base is defined as a proton acceptor, meaning it can accept hydrogen ions (H+) from other substances. This distinguishes it from a proton donor, which is a Brønsted-Lowry acid.

What is the result when an Arrhenius acid and a base combine?

• Water and a salt

• Hydrogen gas

• Oxygen and water

• Carbon dioxide

Answer explanation

When an Arrhenius acid reacts with a base, they undergo neutralization, producing water and a salt. This is a fundamental reaction in acid-base chemistry, confirming that the correct answer is water and a salt.

What is the purpose of a titration in a chemical experiment?

• To measure the temperature of a solution

• To determine the concentration of an acid or base solution

• To change the color of a solution

• To increase the volume of a solution

Answer explanation

The purpose of a titration is to determine the concentration of an acid or base solution by gradually adding a titrant until the reaction reaches completion, indicated by a color change or other measurable endpoint.

Tags

NGSS.HS-PS1-5

What is the role of an indicator in a titration experiment?

• To react with the titrant

• To participate in the neutralization reaction

• To visualize the equivalence point

• To change the pH of the solution

Answer explanation

The role of an indicator in a titration experiment is to visualize the equivalence point. It changes color at a specific pH, signaling that the reaction is complete, allowing the experimenter to determine when to stop adding the titrant.

What is the role of phenolphthalein in a titration involving acetic acid and sodium hydroxide?

• It acts as a reactant.

• It acts as a catalyst.

• It acts as an indicator.

• It acts as a solvent.

Answer explanation

In the titration of acetic acid and sodium hydroxide, phenolphthalein serves as an indicator. It changes color at the endpoint, signaling when the reaction is complete, thus helping to determine the concentration of the acid.