JEE Main 2023 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 6 April 2023, Shift 2, Chemistry Q83

Question 83 of 90 in this shift, Chemistry question 23 of 30, Section B.

Consider the following data Heat of combustion of

\mathrm{H_2(g)}

-241.8

kJ mol

^{-1}

Heat of combustion of

\mathrm{C(s)}

-393.5

kJ mol

^{-1}

Heat of combustion of

\mathrm{C_2H_5OH(l)}

-1234.7

kJ mol

^{-1}

The heat of formation of

\mathrm{C_2H_5OH(l)}

is (

-

)______________ kJ mol

^{-1}

(Nearest integer).

Official answer

278

NTA final key.

Chapter: Thermodynamics (Chemistry)
Topic: Enthalpy and Hess's Law
Idea tested: Formation and Combustion

Same idea in other shifts

Asked 7× in all

8 Apr 2026, Shift 2 · Q74Consider the reaction $2\mathrm{H_2S(g)} + 3\mathrm{O_2(g)} \rightarrow 2\mathrm{H_2O(l)} + 2\mathrm{SO_2(g)}$ The magnitude of enthalpy…EasyNumerical value
5 Apr 2024, Shift 2 · Q83Combustion of 1 mole of benzene is expressed at $\mathrm{C_6H_6(l) + \frac{15}{2}\,O_2(g) \rightarrow 6\,CO_2(g) + 3\,H_2O(l)}$ . The…MediumNumerical value
29 Jul 2022, Shift 2 · Q63 $\mathrm{C(s)} + \mathrm{O_2(g)} \rightarrow \mathrm{CO_2(g)} + 400\ \mathrm{kJ}$ …MediumSingle correct
24 Jun 2022, Shift 2 · Q64At 25°C and 1 atm pressure, the enthalpies of combustion are given below: Substance | H $_2$ | C (graphite) | C $_2$ H $_6$ (g)…MediumSingle correct
25 Jun 2022, Shift 2 · Q62At 25°C and 1 atm pressure, the enthalpy of combustion of benzene (l) and acetylene (g) are -3268 $\mathrm{kJ\ mol^{-1}}$ and -1300…MediumSingle correct
22 Jul 2021, Shift 2 · Q54If the standard molar enthalpy change for combustion of graphite powder is $-2.48 \times 10^2$ kJ mol $^{-1}$ , the amount of heat generated…EasyNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.