Answer to Question #158526 in General Chemistry for Sage Topaz

Question

A 2.5 g sample of KClO₃was heated. The liberated oxygen gas was collected over water at 24 degree Celsius and 755 millimeter Hg. What was the mass and volume of the oxygen gas collected in the set up?

 2KClO ₃ → 2KCl   +   3 O₂ 

Answer 1

2KClO3 → 2KCl + 3 O2

So,

2 moles of KClO3 produce 3 moles O2

Molar mass of KClO3 = 122.55 g/mol

Molar mass of O3 = 32 g/mol

So,

(122.55×2)g KClO3 produce (32×3)g O2

2.5 g KClO3 produce = (96×2.5/245.1) g O2

= 0.9792 g O2

So, mass of oxygen gas produce = 0.9792 g

0.9792 g O2 = (0.9297/32) mol O2

So, number of moles, n = (0.9297/32) mol

Temperature, T = (24+273)K

= 297 K

Pressure,P = 755 mmHg

= (755/760) atm

R= 0.082 L.atm/(mol.K)

We know,

PV = nRT

Or, V = nRT/P

= [(0.9297/32)×0.082×297]÷(755/760)

= 0.712 L

So, mass of oxygen gas produce = 0.9792 g

volume of the produced oxygen gas = 0.712 L