Question icon
Grade 12th passPhysical Chemistry

When 1 mole A reacts with ½ mole of B2 (A + ½B2 = AB), 100 Kcal heat is liberated and when 1 mole of A reacts with 2 mole of B2( A + 2B2= AB4), 200 Kcal heat is liberated . When1 mole of A is completely reacted with excess, of B2 to form AB as well as AB4, 140 Kcal heat is liberated calculate the mole of B2 used.

Profile image of Pranav Dabhade
9 Years agoGrade 12th pass
Answers icon

2 Answers

Profile image of Vikas TU
9 Years ago
(A + ½B2 = AB) => 100kcal
(A +2B2 = AB4) => 200kcal
Adding both chemical eqns. we get,
2A + 5/2 B2  -------->  1/2AB   +  1/2AB4
OR
A + 5/4 B2  -------->  1/4AB   +  1/4AB4
Total Energy = 100 + 200 = 300 kcal.
 
For original reacn.
 
The energy releases = 140 kcal.
Now for 140 kcal let x be the moles of B2 used then,
then x = > 140 x 5/4 / 300 = > 7/12 moles.
Profile image of somay agarwal
4 Years ago
( A + ½ B2 = AB ) => 100 Kcal 
( A + 2 B2 = AB4 ) => 200 Kcal 
 
Adding both chemical eqns. we get,
2A + 5/2 B2  -------->  AB   +  AB4
OR
A + 5/4 B2  -------->  1/2AB   +  1/2AB4
Total Energy = 100 + 200 = 300 kcal.
 
For original reacn.
 
The energy releases = 140 kcal.
Now for 140 kcal let x be the moles of B2 used then,
x = (140 * 5/2)/300 
x ≈ 1.1