Question

Consider the following statements: Statement I: Silica in its normal form is almost non-reactive because of very high Si-O bond enthalpy.  Statement - II: Silica has no reaction with HF.  The correct answer is:

• A. Both the statements I & II are correct.
• B. Statement I is correct but statement - II is NOT correct.
• C. Statement I is NOT correct but statement - II is correct.
• D. Both the statements I & II are NOT correct.

Hint:

Silica resists nearly all acids except HF, which attacks it readily due to the strong affinity between silicon and fluorine.

Answer 1

The Correct Option is B

Step 1: Read both statements.
Statement I says silica is almost non-reactive because of the very strong Si-O bond. Statement II says silica does not react with HF. We must judge each one.

Step 2: Check statement I.
Silica $SiO_2$ is a giant covalent network with very strong Si-O bonds. This strength makes it unreactive towards most acids and halogens at normal temperature. So statement I is correct.

Step 3: Check statement II.
Although silica is generally inert, it does react with hydrofluoric acid. This is a well-known exception.

Step 4: Write the reaction.
Silica reacts with HF as \[ SiO_2 + 4HF \longrightarrow SiF_4 + 2H_2O \] This reaction is why HF is used to etch glass.

Step 5: Judge statement II.
Since silica clearly does react with HF, statement II, which says there is no reaction, is wrong.

Step 6: Combine the results.
Statement I is correct and statement II is not correct. \[ \boxed{\text{I correct, II not correct}} \]