Assertion: The borax `Na_(2)[B_(4)O_(5)(OH)_(4)].8H_(2)O` is a useful primary standard for titrating against acids.
Reason: Aqueous solution of borax contains equal ammounts of weak acid and its salt.

Options

A. If both assertion and reason are true and the reason is the correct explanation of teh assertion.
B. If both assertion and reason are true but reason in not the correct explation of the assertion.
C. If assertion is true but reason is false.
D. Ifassertion is false but reason is true.

Answer

A

Explanation

Assertion: `Na_(2)[B_(4)O_(5)(OH)_(4)].8H_(2)O+2HClto2NaCl+4H_(3)BO_(3)+5H_(2)O`
Indicator methyle orange `pH` range `3.1-4.4`
In water, borax gives both `B(OH)_(3)` and `[B(OH)_(4)]^(-)` and only the `[B(OH)_(4)]^(-)` reacts with `HCl`
Reason: `[B_(4)O_(5)(OH)_(4)]^(2-)+5H_(2)OhArr underset("weak acid")(3B(OH)_(3))+underset("its salt")(2[B(OH)_(4)])`
thus acts a buffer.