Topic: Hess's law and enthalpies of reactions (bond dissociation, combustion, formation etc.)· Chemical Thermodynamics

C(s) + 2H_2(g) → CH_4(g); Δ H = -74.8 kJ mol^-1Which of the following diagrams gives an accurate representation of the above reaction? [R → reactants; P → products]

\(\mathrm{C(s) + 2H_2(g) \to CH_4(g)}\); \(\Delta H = -74.8\) kJ \(\mathrm{mol^{-1}}\)

Which of the following diagrams gives an accurate representation of the above reaction? [R \(\to\) reactants; P \(\to\) products]

Four energy vs reaction progress diagrams (1)-(4) with R, P, 74.8 kJ/mol arrow; options are the diagrams

1. Energy diagram (1)

2. Energy diagram (2)

3. Energy diagram (3)

4. Energy diagram (4)

Doubtly Asked 30 Oct 2026 NEET UG 2025 Practice test neet Save WhatsApp Report

1 answer

Best answer

Answer: 1. Energy diagram (1)

Key idea: \(\Delta H=-74.8\) kJ/mol means an exothermic reaction: products lie 74.8 kJ below the reactants.

Diagram (1) shows P lower than R with the 74.8 arrow spanning the gap between the R and P levels. Diagrams (2) and (4) show P above R (endothermic), and in (3) the arrow measures the barrier height rather than the difference in enthalpy. Option (1).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

Was this answer helpful?

C(s) + 2H_2(g) → CH_4(g); Δ H = -74.8 kJ mol^-1Which of the following diagrams gives an accurate representation of the above reaction? [R → reactants; P → products]

1 answer

Your answer