What volume of oxygen at STP is required to affect the combustion of 11 litres of ethylene at 273°C and 380 mm of Hg pressure? 

Answer in my book : 8.25 litres

 

Asked by singhamaya63 | 24th Feb, 2020, 11:50: AM

Expert Answer:

Given:
 
P = 380 mmHg
 
   = 0.5 atm
 
T = 273 °C
 
   = 273+273
 
   = 546 K
 
V = 11 litre
 
No. of moles = n
 
We have,
 
PV = nRT
 
0.5 space cross times space 11 space equals space straight n cross times 0.0821 cross times 546

straight n equals space fraction numerator 0.5 cross times 11 over denominator 0.0821 cross times 546 end fraction

space space equals 0.122 space mol
 
The reaction is :
 
straight C subscript 2 straight H subscript 4 space space space plus space space 3 straight O subscript 2 space rightwards arrow space 2 CO subscript 2 space space plus space space 2 straight H subscript 2 straight O
1 space vol space space space space space space space space 3 space vol space space space space space 2 space vol space space space space space space space space space 2 space vol
 
 
So for 1 mol of C2H4 combines with 3 mol of O2
 
Now 0.122 moles of C2 H4  will combine with 0.122×3
 
                                                                = 0.368 mol
 
Volume of 1 mole of gas is 22.4 litre
 
Volume of 0.368 mol = 22.4 × 0.368 
 
                               = 8.24 litre
 
Volume of oxygen is 8.24 litre.

Answered by Ravi | 24th Feb, 2020, 12:40: PM