Answer to Question #194289 in General Chemistry for Jmae

Question

Calculate the heat hydrogenation of ethane, C2H4 given the following thermochemical equations:

2C(graphite)+3 H2 (g)-----> C2H6 (g) ∆Hf= -84.5 kJ/mol

2C(graphite)+2 H2 (g)-----> C2H4 (g) ∆Hf= 52.3kJ/mol

Answer 1

Ans:-Target Equation

$C_2H_4 + H_2 \to C_2H_6$

$2C(graphite)+3 H_2 (g)\to C_2H_6 (g) ∆Hf= -84.5 kJ/mol$................(i)

$2C(graphite)+2 H_2 (g)\to C_2H_4 (g) ∆Hf= 52.3kJ/mol$ ....................... (ii)

$\therefore$ To make main equation

$\Rightarrow Eq^n(i)-Eq^n(ii)\\ \Rightarrow \Delta H=\Delta H_1-\Delta H_2\\ =-84.5-52.3\\ =-136.8kJ/mol$