The standard enthalpy of formation of C2H4(g), CO2(g) and H2O(l) are 52, -394 and -286 kJ mol-1 respectively. Then the amount of heat evolved by burning 7 g of C2H4(g) is

Question

The standard enthalpy of formation of C2H4(g), CO2(g) and H2O(l) are 52, -394 and -286 kJ mol-1 respectively. Then the amount of heat evolved by burning 7 g of C2H4(g) is (A) 1412 kJ (B) 9884 kJ (C) 353 kJ (D) 76 kJ

Tardigrade Admin · Accepted Answer

Given, C+O2 arrow CO2 ; Î Hf = -394 kJ mol-1 ...(i) H2 +(1/2)O2 arrow H2O ;ÎHf = -286 kJ mol-1 ...(ii) 2C+2H2 arrow C2H4 ; Î Hf = 52 kJ mol-1 ...(iii) Required equation: C2H4 +3O2 arrow 2CO2 +2H2O ;ÎH = ? ... (iv) To get the equation (iv), multiply equation (i) by 2, multiply equation (ii) by 2 and subtract equation (iii) (i) × 2 + (ii) × 2 - (iii) = iv ÎH = (-3× 4) × 2 + (-286) × 2 - 52 = -1412 kJ 28 g of C2H4 gives 1412 kJ heat 7 g C2H4 will give (1412×7/28)=353 kJ

Q. The standard enthalpy of formation of $C_{2} H_{4 (g)}, C O_{2 (g)}$ and $H_{2} O_{(l)}$ are $52, - 394$ and $- 286 k J m o l^{- 1}$ respectively. Then the amount of heat evolved by burning $7 g$ of $C_{2} H_{4 (g)}$ is

$1412 k J$

$9884 k J$

$353 k J$

$76 k J$

Q. The standard enthalpy of formation of C2​H4(g)​,CO2(g)​ and H2​O(l)​ are 52,−394 and −286kJmol−1 respectively. Then the amount of heat evolved by burning 7g of C2​H4(g)​ is

1412kJ

9884kJ

353kJ

76kJ

Q. The standard enthalpy of formation of $C_{2} H_{4 (g)}, C O_{2 (g)}$ and $H_{2} O_{(l)}$ are $52, - 394$ and $- 286 k J m o l^{- 1}$ respectively. Then the amount of heat evolved by burning $7 g$ of $C_{2} H_{4 (g)}$ is

$1412 k J$

$9884 k J$

$353 k J$

$76 k J$