Understanding Acid Properties: Taste and Indicators

Let's analyze the given statements about acids to determine which one accurately describes their properties.

Statement I: Acid is sour in taste

This statement refers to the taste of acids. Many common acids found in food products are known for their sour taste. For example, citric acid in lemons and oranges, tartaric acid in tamarind, and acetic acid in vinegar are all acids that give food a sour flavour. While tasting chemicals in a lab is dangerous and should never be done, the sour taste is a characteristic property of many acids, especially edible ones.

Statement II: Acid turns red litmus paper into blue

This statement describes the effect of a substance on litmus paper, which is a common acid-base indicator. Litmus paper comes in two colours: red and blue. Acids are known to turn blue litmus paper red. Conversely, bases are substances that turn red litmus paper blue. Therefore, the statement that an acid turns red litmus paper into blue is incorrect; this describes the action of a base, not an acid.

Conclusion based on Acid Properties

Based on the analysis of the two statements:

• Statement I correctly describes a common property of acids (sour taste).
• Statement II incorrectly describes the effect of an acid on litmus paper (it describes the effect of a base).

Therefore, only Statement I is a correct description of an acid's property from the given options.

Detailed Analysis of Options

Let's examine the provided options in light of our conclusion:

• Option 1: "Only I is correct" - This aligns with our finding that Statement I is correct and Statement II is incorrect.
• Option 2: "Only II is correct" - This is incorrect because Statement II is false.
• Option 3: "Both I and II" - This is incorrect because Statement II is false.
• Option 4: "None of these is correct" - This is incorrect because Statement I is correct.

Thus, the correct option is the one stating that only Statement I is correct.

Revision Table: Key Properties of Acids and Bases

Additional Information on Acids and Bases

Acids and bases are fundamental concepts in chemistry, defined by their behaviour in water and their interaction with indicators and other substances.

• Definitions: Acids are substances that typically donate protons (\(\text{H}^+\) ions) or accept electrons. In water, they increase the concentration of hydronium ions (\(\text{H}_3\text{O}^+\)). Bases typically accept protons or donate electrons. In water, they increase the concentration of hydroxide ions (\(\text{OH}^-\)).
• Indicators: Substances like litmus, phenolphthalein, and methyl orange are called acid-base indicators because they change colour depending on whether they are in an acidic or basic solution. This colour change helps us identify the nature of a solution without tasting it.
• pH Scale: The pH scale is used to measure the acidity or basicity of a solution. It ranges typically from 0 to 14. Solutions with pH less than 7 are acidic, pH equal to 7 are neutral (like pure water), and pH greater than 7 are basic.
• Strength: Acids and bases can be strong or weak depending on how completely they ionize in water. Strong acids (like hydrochloric acid, \(\text{HCl}\)) ionize almost completely, while weak acids (like acetic acid, \(\text{CH}_3\text{COOH}\)) ionize only partially.

Understanding these properties and tests helps in identifying and working with acids and bases safely and effectively in various applications, from everyday life to industrial processes.