Question

The order of increasing acidic strength for boron hydrides is:

• A. $B_5{H}_9<B_6{H}_{10}<B_{10}{H}_{14}$
• B. $B_{10}{H}_{14}<B_5{H}_9<B_6{H}_{10}$
• C. $B_6{H}_{10}<B_{10}{H}_{14}<B_5{H}_9$
• D. $B_{10}{H}_{14}<B_6{H}_{10}<B_5{H}_9$

Answer 1

The correct option is A $B_5{H}_9<B_6{H}_{10}<B_{10}{H}_{14}$

Acidic strength of boranes increases with an increase in size (i.e. the number of boron atoms). This is because of greater delocalisation of charge in the large clusters. As $B_{10}{H}_{14}$ is the bulkiest molecule, it will have the highest acidic strength.