Download App

5. Thermodynamics and thermochemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry5. Thermodynamics and thermochemistry1 Mark
MCQ
At $25^{\circ} C$ and 1 atm pressure, the enthalpies of combustion are as given below:

Substance $H _{2}$ $C ($ graphite $)$ $C _{2} H _{6}( g )$
$\frac{\Delta_{ C } H ^{\Theta}}{ kJmol ^{-1}}$ $-286.0$ $-394.0$ $-1560.0$

The enthalpy of formation of ethane is ........ .

  • A
    $+54.0\, kJ \,mol ^{-1}$
  • B
    $-68.0 \,kJ \,mol ^{-1}$
  • ✓
    $-86.0\, kJ \,mol ^{-1}$
  • D
    $+97.0\, kJ \,mol ^{-1}$
✓

Answer

Correct option: C.
$-86.0\, kJ \,mol ^{-1}$
c
$C _{2} H _{6}( g )+\frac{7}{2} O _{2}( g ) \rightarrow 2 CO _{2}( g )+3 H _{2} O (\ell)$

$\Delta_{ C } H \left( C _{2} H _{6}\right)=2 \Delta_{ f } H CO _{2}( g )+3 \Delta_{ f } H \left( H _{2} O , \ell\right)$

$-\Delta_{ f } H ^{\prime}\left( C _{2} H _{6}, g \right)$

$-1560=2(-394)+3(-286)-\Delta_{ f } H \left( C _{2} H _{6}, g \right)$

$\Delta_{ f } H \left( C _{2} H _{6}, g \right)=-86 \,kJ / mole$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "M.C.Q (1 Marks)" from 5. Thermodynamics and thermochemistry→5. Thermodynamics and thermochemistry — all question types→Chemistry STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

If Hund's Rule does not hold good, then which of the following pairs is diamagnetic
→
Which of the following carbocation is least stable
→
In which of the following processes energy is absorbed?
→
Which of petroleum corresponds to kerosene oil
→
The ratio between kinetic energy and the total energy of the electrons of hydrogen atom according to Bohr’s model is
→
Chlorination of benzene is not possible in the following reaction
→
A dibromo derivative of an alkane reacts with sodium metal to form an alicyclic hydrocarbon.
The derivative is ___________ .
→
$2 O _{3}( g ) \rightleftharpoons 3 O _{2}( g )$

At $300 \,K$, ozone is fifty percent dissociated. The standard free energy change at this temperature and $1\, atm$ pressure is $(-)$ $........\,J\, mol ^{-1}$ (Nearest integer)

[Given: $\ln 1.35=0.3$ and $R =8.3 J K ^{-1} mol ^{-1}$ ]

→
The interatomic distances in ${H_2}$ and $C{l_2}$ molecules are $74$ and $198$ $pm$ respectively. The bond length of $HCl$ is ............. $\mathrm{pm}$
→
Find out the number of $1-2$-shifts during the conversion of
→