1. Tardigrade
  2. Question
  3. Chemistry
  4. Consider the reactions given below. On the basis of these reactions find out which of the algebric relations given in options (a) to (d) is correct? (i) C(g)+4H(g) → CH4(g); ΔrH = x kJ mol-1 (ii) C(graphite, s)+2H2(g) → CH4(g); ΔrH = y kJ mol-1

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Q. Consider the reactions given below. On the basis of these reactions find out which of the algebric relations given in options $(a)$ to $(d)$ is correct?
(i) $C_{\left(g\right)}+4H_{\left(g\right)} \to CH_{4\left(g\right)}; \Delta_{r}H = x\,kJ\,mol^{-1}$
(ii) $C_{\left(graphite,\,s\right)}+2H_{2\left(g\right)} \to CH_{4\left(g\right)}; \Delta_{r}H = y\,kJ\,mol^{-1}$

Thermodynamics

Solution:

In eqn $(i)$, no bond is being broken while in eqn $(ii)$, $2\, H-H$ bonds are broken. So, in eqn $(ii)$ some of the energy is used up to break the bonds. Thus, $x > y$.