NEET UG CHEMISTRY MCQ: THERMODYNAMICS

1 Hard

1 of 1

Application +4 | -1

The heat evolved on combustion of

1 \, \mathrm{gm}

of starch,

\left({C}_6 {H}_{10}{O}_5\right)

, into

{CO}_2({g})

and

{H}_2 {O}({l})

4.18 \, \text{Kcal}.

What is the standard enthalpy of formation of

1 \, \mathrm{gm}

of starch? Heat of formation of

{CO}_2({g})

and

{H}_2 {O}({l})

are

-94.05

and

-68.32 \, \mathrm{Kcal} / \mathrm{mol}

View answer and explanation

Correct option: C

-1.41 \, \mathrm{Kcal}

Option C (

-1.41 \text{ Kcal}

) is correct because it is calculated by using the heat of combustion of starch and the heats of formation of CO2 and H2O to find the standard enthalpy of formation of starch.

More Questions from THERMODYNAMICS

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The internal energy of one mole of a gas is: An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If

{T_i}

is the initial temperature and

{T_f}

is the final temperature, which of the following statements is correct? For which of the process, ∆S is negative? The work done by a weightless piston in causing an expansion ∆V (at constant temperature), when the opposing pressure, P is variable, is given by: Assertion :- At constant pressure of the change

\mathrm{H}_2 \mathrm{O}(\mathrm{s}) \rightarrow \mathrm{H}_2 \mathrm{O}(\mathrm{g})

work done is negative.

Reason :- During phase transition work done is always negative. For the reaction,

\mathrm{X}_2 \mathrm{O_4(l}) \longrightarrow 2 \mathrm{XO}_2(\mathrm{g}), \Delta U=2.1 \mathrm{~kcal}, \Delta S=20 \mathrm{~cal} \mathrm{~K}^{-1}

300 \mathrm{~K}

. Hence,

\Delta G