Answer:
D. They react readily with oxygen in the air
The number of moles in monochloro pentaborane (9)
is 0.37056.
We know that ,
Number of moles = Given mass/ Molar mass
Given mass of monochloro pentaborane (9) is 20.1 g
The molar mass of monochloro pentaborane (9) is
= 
= 
= 54.241
Thus number of moles = 20.1/54.241
= 0.37056
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Answer:
I think it may be b but I am not sure