Question

How many grams of CaH₂ are needed to generate 144 L of H₂ gas if the pressure of H2 is 827 torr at 20^oC?

Answer 1

first find the moles of H2 using

PV = nRT formula

P = pressure = 827 torr convert in to atm = 1.088 atm

V = volume = 144 L

n = no fo moles we have to calculate

R = gas constant = 0.0821 L atm mol-1 K-1

T = 273+20 = 293K

1.08 atm x 144 L = n 0.0821 x 293 K

n = 156.672 / 24.0553

= 6.513 mol

now lets write th ebalanced equation

CaH2 (s) + 2H2O (l) ----> Ca(OH)2 + 2H2

from the balanced equation

1 mole of CaH2 is producing 2 mole of H2 accordingly

how many moles of CaH2 produces 6.513 mol of H2

= 6.513 mol / 2

= 3.256 mol

mass of CaH2 = moles x molar mass = 3.256 mol x 42.094 g/mol

= 137.08 g