Question

Borax dissolves in water and forms a product of boron \((X)\). Identify the compound \(X\).

• A. \(HBO_2\)
• B. \(B_2O_3\)
• C. \(NaBO_2\)
• D. \(H_3BO_3\)

Hint:

Borax hydrolyses in water to form boric acid \((H_3BO_3)\), which is a weak monobasic Lewis acid.

Answer 1

The Correct Option is D

Step 1: Write the formula of borax.
Borax is sodium tetraborate decahydrate: \( Na_2B_4O_7 \cdot 10H_2O \).
Step 2: State what happens on dissolving in water.
Borax hydrolyses in water. The tetraborate ion breaks down into sodium hydroxide and boric acid.
Step 3: Write the hydrolysis reaction.
\[ Na_2B_4O_7 + 7H_2O \rightarrow 2NaOH + 4H_3BO_3 \] The boron-containing product is boric acid.
Step 4: Identify compound X.
The boron product is \( H_3BO_3 \) (boric acid).
Step 5: Verify against options.
The four choices are \( HBO_2 \), \( B_2O_3 \), \( NaBO_2 \), and \( H_3BO_3 \). Option 4 matches our product \( H_3BO_3 \).
Step 6: Confirm the answer.
Borax dissolves in water to give boric acid as the boron product. \[ \boxed{H_3BO_3} \]