Bond enthalpies of H2, X2 and HX are in the ratio 2 : 1 : 2, if enthalpy of formation of HX is -50kJ mol-1, the bond enthalpy of X2 is ?

Question

Bond enthalpies of $H_{2}, X_{2}$ and $H X$ are in the ratio 2 : 1 : 2, if enthalpy of formation of $H X$ is $- 50 k J m o l^{- 1}$ , the bond enthalpy of $X_{2}$ is ?

Smart Achievers · Accepted Answer

(1)

$\frac{1}{2} H_{2} + \frac{1}{2} X_{2} \to H X Δ H = - 50$

$2 a$ $X_{2}$ $2 a$

$\frac{2 a}{2} + \frac{a}{2} - 2 a = - 50$

$3 a - 4 a = - 100$

$a = 100$

Solution

Q.
Bond enthalpies of $H_{2}, X_{2}$ and $H X$ are in the ratio 2 : 1 : 2, if enthalpy of formation of $H X$ is $- 50 k J m o l^{- 1}$ , the bond enthalpy of $X_{2}$ is

1 $100 k J m o l^{- 1}$

2 $300 k J m o l^{- 1}$

3 $200 k J m o l^{- 1}$

4 $400 k J m o l^{- 1}$

Ans.
(1)

$\frac{1}{2} H_{2} + \frac{1}{2} X_{2} \to H X Δ H = - 50$

$2 a$ $a$ $2 a$

$\frac{2 a}{2} + \frac{a}{2} - 2 a = - 50$

$3 a - 4 a = - 100$

$a = 100$

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Solution

Q. Bond enthalpies of H2, X2 and HX are in the ratio 2 : 1 : 2, if enthalpy of formation of HX is -50 kJ mol-1, the bond enthalpy of X2 is

1 100 kJ mol-1

2 300 kJ mol-1

3 200 kJ mol-1

4 400 kJ mol-1

Ans. (1) 12H2+12X2→HX ΔH=-50 2a a 2a 2a2+a2-2a=-50 3a-4a=-100 a=100