Question

$A$ and $B$ are formed when borax is dissolved in water. $C$ and $B$ are formed when borax is reacted with aqueous $HCl$ solution. What are $A$ and $C$ respectively?

• A. $NaCl,NaOH$
• B. $NaOH,NaCl$
• C. $NaB{O}_2,NaCl$
• D. $NaOH,NaB{O}_2$

Answer 1

Answer: (B)

The reaction of borax $\left(N{a}_2{B}_4{O}_7\right)$ with water occurs as follows:

$N{a}_2{B}_4{O}_7+7H_{2}O⟶\underset{(B)}{4H_{3}B{O}_3}+\underset{(A)}{2NaOH}$

While, borax reacts with $HCl$ (dil.) as follows:

$N{a}_2{B}_4{O}_7+2HCl($ dil. $)⟶2NaCl+4\left[B\left(H_{2}O\right)(OH{)}_3\right]$

Or
$N{a}_2{B}_4{O}_7+2HCl+9H_{2}O⟶\underset{C)}{2NaCl}+4\left[B\left(H_{2}O\right)(OH{)}_3\right]$

or, $N{a}_2{B}_4{O}_7+2HCl\cdot l0H_{2}O⟶\underset{(B)}{4H_{3}B{O}_3}+\underset{(C)}{2NaCl}+5H_{2}O$

Hence, $(A)=NaOH$ and $(C)=NaCl$