Question

when 12 g carbon reacted with O2 to form CO and CO2 at 25°C and const pressure, 75 kcal of heat was liberated and no carbon remained. then the mass of O2 reacted is (given dH CO2 =-95kcal and dH CO =-24kcal

Answer 1

Dear friend,

Given data:

C +34 O2 →12CO2 + 12CO ∆H=−75 kcal/mol

C + O2 → CO2 ∆H=−94.05 kcal/molC + 12O2 → CO ∆H= −26.41 kcal/mol

I.

12 g of carbon reacts with 32 g of oxygen to form CO2

y g of carbon will react with 3212y g of oxygen to form CO2

Similarly

12 g of carbon reacts with 16 g of oxygen to form CO

(12 − y) g of carbon will react with 1612(12−y) g of oxygen to form CO.

Since mass of oxygen required in the reaction is 4x, therefore,

3212y +1612(12−y)=4x 32 y + 16(12−y) =48 x 2y + 12 − y = 3x 3x − y = 12 −−−−−(1)

II.

Energy produced when 12 g of carbon reacts with oxygen to form CO2= −94.05 kcal

Energy produced when y g of carbon reacts with oxygen to form CO2 = −94.0512y kcal

Similarly,

Energy produced when 12 g of carbon reacts with oxygen to form CO= − 26.41 kcal

Energy produced when (12 − y) g of carbon reacts with oxygen to form CO = −26.4112(12−y) kcal

Since, total enthalpy of formation is −75 kcal/mol, therefore,

−94.0512y − 26.4112(12−y) = −75

−94.05y − 316.92 + 26.41y = −900 −67.64y = − 583.08 y = 8.62

From (1) equation, value of x can be calculated as

3x − 8.62 = 12

x = 6.87

Thus, the value of x is 6.87.

Hope this information will clear your doubts.

If you have any more doubts just ask me

Regards,