Question

Which of the following equations represent the standard heat of formation of $C_2{H}_4$?

• A. $2C\text{(diamond)}+2H_2\left(g\right)\to C_2{H}_4\left(g\right)$
• B. $2C\text{(graphite)}+2H_2\left(g\right)\to C_2{H}_4\left(g\right)$
• C. $2C\text{(diamond)}+4H\left(g\right)\to C_2{H}_4\left(g\right)$
• D. $2C\text{(graphite)}+4H\left(g\right)\to C_2{H}_4\left(g\right)$

Answer 1

The correct option is B $2C\text{(graphite)}+2H_2\left(g\right)\to C_2{H}_4\left(g\right)$

Standard heat of formation of $C_2{H}_4$ is the heat change when 1 mole of $C_2{H}_4$ is formed from its elements in the standard state, i.e carbon as graphite and hydrogen as $H_2$.
Therefore, the correct option is $\left(b\right)$.