Question

Consider the following reactions \[ \text{Borax} \xrightarrow{\mathrm{H_2O}} A+B \] \[ \text{Borax} \xrightarrow[\mathrm{HCl}]{\mathrm{H_2O}} B+C \] Which of the following are the properties of \(A\), \(B\), \(C\)? \[ \begin{aligned} \text{I. }& \text{Both }A,B\text{ are strong bases} \text{II. }& B\text{ is a white crystalline solid with soapy touch} \text{III. }& C\text{ is water soluble} \end{aligned} \] The correct answer is

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

Hint:

Remember the hydrolysis of borax: \[ \boxed{ \mathrm{Na_2B_4O_7+7H_2O \rightarrow 2NaOH+4H_3BO_3} } \] Here, \[ \boxed{ \mathrm{NaOH} } \] is a strong base, whereas \[ \boxed{ \mathrm{H_3BO_3} } \] is a weak Lewis acid.

Answer 1

The Correct Option is B

Step 1: Write the reactions of borax. On hydrolysis, \[ \mathrm{Na_2B_4O_7+7H_2O \rightarrow 2NaOH+4H_3BO_3.} \] Thus, \[ A=\mathrm{H_3BO_3}, \qquad B=\mathrm{NaOH}. \] In the presence of hydrochloric acid, \[ \mathrm{Na_2B_4O_7+2HCl+5H_2O \rightarrow 2NaCl+4H_3BO_3.} \] Hence, \[ C=\mathrm{H_3BO_3}. \]

Step 2: Check the given statements. \[ A=\mathrm{H_3BO_3} \] is a weak acid, not a strong base. Therefore, Statement I is incorrect. \[ B=\mathrm{NaOH} \] is a white crystalline solid having a soapy touch. Hence, Statement II is correct. Boric acid, \[ \mathrm{H_3BO_3}, \] is soluble in water. Thus, Statement III is also correct.

Step 3: Choose the correct option. Therefore, \[ \boxed{\text{Only Statements II and III are correct}.} \] Hence, the correct option is \(\boxed{(B)}\).