Question

Consider the following chemical reaction: 2H2O(l)→2H2(g)+O2(g) What mass of H2O is required to form 1.5 L of O2 at a temperature of 325 K and a pressure of 0.946 atm ? Express your answer using two significant figures.

Answer 1

PV = nRT

where, P = 0.946 atm

V = 1.5 L

n = number of moles

R = Gas constant

T = 325 K

0.946 * 1.5 = n * 0.0821*325

1.42 = n * 26.7

n = 1.42 / 26.7 = 0.0532 mole

Therefore, number of moles of O2 = 0.0532 mole

From the balanced equation we can say that

1 mole of O2 requires 2 mole of H2O so

0.0532 mole of O2 will require

= 0.0532 mole of O2 *(2 mole of H2O / 1 mole of O2)

= 0.106 mole of H2O

mass of 1 mole of H2O = 18.016 g so

the mass of 0.106 mole of H2O = 1.9 g

Therefore, the mass of H2O required would be 1.9 g