Assertion : Ammonia solution is an alkali.Reason : Ammonia solution t...
Assertion: Ammonia solution is an alkali.
Reason: Ammonia solution turns blue litmus paper red.
The correct answer is option 'C' - Assertion (A) is true but reason (R) is false.
Explanation:
Assertion: Ammonia solution is an alkali.
Reason: Ammonia solution turns blue litmus paper red.
To evaluate the given assertion and reason, let's understand the definitions of alkali and litmus paper.
Alkali:
An alkali is a type of chemical compound that is soluble in water and produces hydroxide ions (OH-) when dissolved. Alkalis are also known as bases. Examples of alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)2).
Litmus Paper:
Litmus paper is a pH indicator used to determine whether a substance is acidic, basic, or neutral. It comes in two colors: blue and red. Blue litmus paper turns red in the presence of an acid and remains blue in the presence of a base/alkali.
Explanation of Assertion:
The assertion states that ammonia solution is an alkali. However, this is incorrect.
Ammonia solution (NH3) is a weak base, not an alkali. It does not produce hydroxide ions (OH-) when dissolved in water. Instead, it accepts a proton (H+) from water to form ammonium ions (NH4+) and hydroxide ions (OH-). The reaction can be represented as:
NH3 + H2O → NH4+ + OH-
Explanation of Reason:
The reason given is that ammonia solution turns blue litmus paper red. This is true.
When ammonia solution comes into contact with blue litmus paper, it turns the blue litmus paper red. This color change occurs because ammonia solution is a weak base and can react with water to produce hydroxide ions (OH-). These hydroxide ions react with the blue litmus paper, which is an indicator of acidity, and turn it red.
However, it is important to note that the fact that ammonia solution turns blue litmus paper red does not mean that ammonia solution is an alkali. It is a weak base, but not a strong alkali like sodium hydroxide or potassium hydroxide.
Conclusion:
In conclusion, the given assertion is incorrect, and the reason provided is true but does not correctly explain the assertion. Ammonia solution is a weak base, not an alkali, and it turns blue litmus paper red due to the presence of hydroxide ions produced when it reacts with water.
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