A 0070g sample of the boron hydride B4H1o is burned in pure

A 0.070-g sample of the boron hydride, B4H1o, is burned in pure oxygen to give B2Os and H20. 2 B,Ho(s) + 1102 (g) 4 B2O3 + 10 H2O (g) Calculate the pressure of the gaseous water in a 4.05-L flask at 40. °C Pressure =1 mmHg

Solution

mass of B4H10 = 0.070 g

moles of B4H10 = 0.070 / 53.3234 = 1.31 x 10^-3 mol

from the balanced equation :

2 mol B4O10   ---------------> 10 mol H2O

1.31 x 10^-3 mol -------------> ??

moles of water = 1.31 x 10^-3 x 10 / 2

                       = 6.56 x 10^-3 mol

volume = 4.05 L

temperature = 40 oC = 313 K

P V = n R T

P x 4.05 = 6.56 x 10^-3 x 0.0821 x 313

P = 0.0416 atm

pressure = 31.6 mmHg