Why is it important to close the container of sodium borohydride after use in the laboratory?

• A. To prevent the compound from reacting with moisture in the air and decomposing.
• B. To keep the container from absorbing carbon dioxide and forming sodium carbonate.
• C. To prevent the release of flammable vapors into the laboratory.
• D. To avoid contamination with dust, which would make it toxic.

Answer: (A)

Verified step by step guidance

1. Understand the chemical nature of sodium borohydride (NaBH\_4), which is a strong reducing agent and reacts readily with water (moisture) to release hydrogen gas and decompose.
2. Recognize that exposure to moisture in the air causes sodium borohydride to hydrolyze according to the reaction: \(\mathrm{NaBH\_4 + 4H\_2O \rightarrow NaBO\_2 + 4H\_2}\), leading to loss of its reducing ability and potential safety hazards due to hydrogen gas release.
3. Note that keeping the container closed prevents moisture from entering and thus preserves the chemical integrity and effectiveness of sodium borohydride for laboratory use.
4. Consider that while sodium borohydride might also react with carbon dioxide or absorb dust, these are less critical compared to its reaction with moisture, which directly causes decomposition and safety risks.
5. Conclude that the primary reason to close the container is to prevent the compound from reacting with moisture in the air and decomposing, ensuring both safety and chemical stability.