Question

A standard solution of sodium hydroxide cannot be prepared by direct wcighing of cold sodium hydroxide because (1) NaOII is a solid (2) NaOII is a liquid (3) NaOII is casily dissolved (4) NaOII is a deliquescent substance

Short answer

Option (4) - NaOH is a deliquescent substance.

Step-by-step solution

Understand the Problem

We need to determine why a standard solution of sodium hydroxide (NaOH) cannot be prepared by directly weighing cold NaOH.

Analyze the Given Options

Review each of the given options to determine which one correctly describes why NaOH cannot be prepared in this manner.

Review Properties of NaOH

NaOH is known to be deliquescent, which means it can absorb moisture from the air and dissolve in it. This property makes it challenging to obtain an accurate mass by direct weighing.

Correct Option

From the properties reviewed, identify that option (4) – 'NaOH is a deliquescent substance' is the correct reason.

Key concepts

Sodium Hydroxide Properties

Sodium hydroxide (NaOH) is a strong base and a widely used chemical in laboratories and industry. It appears as white crystalline solid and is highly soluble in water, forming a strong alkaline solution. One of its key properties is its exothermic reaction with water, meaning it releases heat. It is also highly corrosive, which requires careful handling.
Sodium hydroxide is used for various applications such as:

• Manufacturing of soaps and detergents
• Water treatment
• Paper production
• Metal processing

These properties make NaOH very valuable, but they also necessitate special consideration when preparing solutions, especially when combined with its deliquescent nature.

Deliquescent Substances

Deliquescent substances are materials that have a high affinity for moisture from the environment. They absorb water vapor from the air until they dissolve in the absorbed water, forming a solution. Sodium hydroxide is an example of a deliquescent substance.
This property poses challenges when attempting to weigh sodium hydroxide accurately. As soon as NaOH is exposed to air, it begins to absorb moisture and partially dissolve, which makes obtaining an accurate mass measurement nearly impossible.
In laboratory settings, precautions need to be taken when handling deliquescent substances:

• Store in airtight containers to prevent contact with moisture
• Weigh in a low-humidity environment if possible
• Minimize the time the substance is exposed to air

Understanding these characteristics helps in accurately preparing and using deliquescent substances.

Accurate Mass Measurement

Accurate mass measurement is crucial in many chemical processes. For standardized solutions, precision in measuring the amount of a substance directly affects the concentration of the solution.
When dealing with substances like sodium hydroxide, which are deliquescent, achieving accurate mass measurements can be difficult. The substance absorbs moisture from the air which adds to its apparent weight. Here are some strategies to ensure more accurate mass measurements:

• Use a desiccator to protect the substance from moisture during weighing
• Tare the weighing container to zero before measuring
• Work quickly in a low-humidity environment

These strategies help mitigate the impact of moisture absorption and ensure more precise mass measurements, ensuring the reliability and accuracy of the standard solutions prepared.