If a 0.050g sample of the boron hydride burns completely in #O_2#, what will be the pressure of the gaseous water In a 4.25-L flask at 30.0°C?

1 Answer
Dec 10, 2015

Answer:

I assume that you mean diborane, #B_2H_6#.
#B_2H_6(g) + 3O_2 rarr B_2O_3(s) + 3H_2O(g)uarr#

Explanation:

You are presumed to have #(0.050*g)/(27.67*g*mol^-1) = ?? mol# diborane.

By the stoichiometry of the reaction listed, for each mole of diborane that combusts, #3*mol# of water are produced.

Assuming ideality, #P# #=# #(nRT)/V# #=# #3xx((0.050*g)/(27.67*g*mol^-1))(xx0.0821*L*atm*K^-1mol^-1xx303K)xx(1/(4.25*L))# #=# #?? atm#.

Why did I use #303*K# instead of the given temperature in Centigrade? Would it make a difference if I used the formula #BH_3# instead of that of diborane?

Please note that this answer rests on the assumption that you mean diborane. There are many other borohydrides.