Verified Solution • 2025–26 Session moderate

QJEEM20Ch2905: JEE Main 2020 Chemistry - Class 11 JEEM20Ch2905 Solution: The heat of combustion of ethanol into carbon dioxide and water …

The heat of combustion of ethanol into carbon dioxide and water is – 327 kcal at constant pressure. The heat evolved (in cal) at constant volume and 27oC (if all gases behave ideally) is (R = 2 cal mol–1 K–1) ________.

Step-by-Step Verified Solution

C2H5OH (l) + 3O2(g) →\to 2CO2(g) + 3H2O(l)

Δ\Delta H = –327 kcal; Δ\Delta ng = – 1

Δ\Delta H = Δ\Delta U + Δ\Delta ngRT

⇒\Rightarrow Δ\Delta U = – 327 + 2 × 10–3 × 300

= – 326.4 kcal

= – 326400 cal

∴\therefore Heat evolved = 326400 cal.

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