Question

Among the following, the correct statements are: 
Statement I – Nature of Saline (Ionic) Hydrides
Statement II – Volatility of Saline Hydrides
Statement III – Nature of Electron-Precise Hydrides
Statement IV – Formula of Chromium Hydride

• A. I, III only
• B. II, IV only
• C. I, IV only
• D. III, IV only

Hint:

Saline hydrides are generally non-volatile due to strong ionic bonding. Electron-precise hydrides do not act as Lewis bases because they lack lone pairs.

Answer 1

The Correct Option is C

Step 1: Understanding Saline Hydrides
Saline hydrides (ionic hydrides) are formed by alkali and alkaline earth metals with hydrogen. Examples: LiH, BeH₂, and MgH₂. These hydrides have a significant ionic character, though lighter ones like BeH₂ and MgH₂ have some covalent character. Thus, Statement I is correct.
Step 2: Are Saline Hydrides Volatile?
Volatility depends on weak intermolecular forces. Saline hydrides form strong ionic bonds, making them non-volatile. Thus, Statement II is incorrect.
Step 3: Understanding Electron-Precise Hydrides
Electron-precise hydrides like CH₄ and SiH₄ have enough valence electrons to form covalent bonds. These are not Lewis bases because they do not have lone pairs to donate. Thus, Statement III is incorrect.
Step 4: Chromium Hydride Formula
Chromium forms a hydride with the formula CrH. Thus, Statement IV is correct.
Step 5: Correct Answer
The correct statements are (I) and (IV). Thus, the correct answer is (C).

Answer 2

Step 1: Nature of Saline (Ionic) Hydrides

Saline hydrides, also known as ionic hydrides, are formed by elements in the alkali metal (Group 1) and alkaline earth metal (Group 2) families when they react with hydrogen. Examples include LiH, NaH, CaH₂, and MgH₂. These compounds consist of metal cations (M⁺) and hydride anions (H⁻), held together by strong ionic bonds.

However, the lighter alkaline earth metal hydrides such as BeH₂ and MgH₂ possess partial covalent character due to the high charge density and small size of the metal ions.

✅ Statement I is correct.

Step 2: Volatility of Saline Hydrides

Volatility refers to a compound’s ability to vaporize easily. Substances with weak intermolecular forces, such as covalent compounds, tend to be more volatile. In contrast, saline hydrides are held together by strong ionic bonds, making them stable solids with high melting points and low vapor pressures.

As a result, they do not readily vaporize and are considered non-volatile.

❌ Statement II is incorrect.

Step 3: Understanding Electron-Precise Hydrides

Electron-precise hydrides, such as CH₄ (methane) and SiH₄ (silane), have the exact number of valence electrons needed to form standard covalent bonds. These molecules lack lone pairs of electrons and thus cannot donate electron pairs to form coordinate bonds.

Therefore, they do not act as Lewis bases.

❌ Statement III is incorrect.

Step 4: Chromium Hydride Formula

Transition metals like chromium can form hydrides under specific conditions. The most common hydride formed by chromium is CrH, where chromium typically exhibits a +1 oxidation state. Although transition metal hydrides are less common, they are known in coordination chemistry and can be important in catalysis.

✅ Statement IV is correct.

Final Conclusion

Based on the above evaluation:

Correct Statements: I and IV
Incorrect Statements: II and III

✅ Correct Answer: (C)