Calculate - f H o in kJ-mol for Cr 2 O 3 from the - r G o and the S o values provided at 27 o C- 4Crs-3 O 2 g- 2 Cr 2 O 3 s - - r G o -2093-4kJ-mol- S o J-Kmol - S o Cr-s-24- S o O 2 -g-205- S o Cr 2 O 3 -s-81

The correct option is D 1129.05kJ/mol As we know, Δ G =Δ H T #160;Δ S; Δ H = #160;Δ G + T #160;Δ S = 2093.42 + 3002× 1000× (2× 81 3× 205 ...

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Standard XII

Mathematics

Existence of Limit

Calculate Δ...

Question

Calculate $Δ_{f} H^{o}$ (in $k J / m o l$ ) for ${C r}_{2} O_{3}$ from the $Δ_{r} G^{o}$ and the $S^{o}$ values provided at $27^{o} C$ .
$4 C r (s) + 3 O_{2} (g) ⟶ 2 {C r}_{2} O_{3} (s)$ ;
$Δ_{r} G^{o} = - 2093.4 k J / m o l$ ; $S^{o} (J / K m o l) : S^{o} (C r, s) = 24; S^{o} (O_{2}, g) = 205; S^{o} ({C r}_{2} O_{3}, s) = 81$

- 2258 k J / m o l

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- 1129.05 k J / m o l

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- 964.35 k J / m o l

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none of these

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Solution

The correct option is D $- 1129.05 k J / m o l$
As we know,
$Δ G = Δ H - T Δ S;$

$Δ H = Δ G + T Δ S = - \frac{2093.4}{2} + \frac{300}{2 \times 1000} \times (2 \times 81 - 3 \times 205 - 4 \times 24) = - 1129.05 k J / m o l$

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Similar questions

For the hypothetical reaction,

A_{2} (g) + B_{2} (g) ⇌ 2 A B (g)

, if

Δ_{r} G^{o}

and

Δ_{r} S^{o}

are

20 k J / m o l

and

- 20 {J K}^{- 1} {m o l}^{- 1}

respectively at 200 K.

Δ_{r} C_{p}

20 J K^{- 1} m o l^{- 1}

Then value

\frac{Δ_{r} H^{o}}{10}

of (

k J / m o l

) at 400 K is:

Q. For the hypothetical reaction:

A_{2} (g) + B_{2} (g) ⇌ 2 A B (g)

Δ_{r} G^{o}

and

Δ_{r} S^{o}

20 k J / m o l

and

- 20 {J K}^{- 1} {m o l}^{- 1}

respectively at

200 K

. If

Δ_{r} C_{p}

20 {J K}^{- 1} {m o l}^{- 1}

then

Δ_{r} H^{o}

400 K

is :

Q. From the data at

25^{o} C

{F e}_{2} O_{3} (s) + 3 C_{g r a p h i t e} ⟶ 2 F e (s) + 3 C O (g); Δ H^{o} = 492 k J / m o l

F e O (s) + C_{g r a p h i t e} ⟶ F e (s) + C O (g); Δ H^{o} = 155.8 k J / m o l

C_{g r a p h i t e} + O_{2} (g) ⟶ C O_{2} (g); Δ H^{o} = - 393.51 k J / m o l

C O (g) + \frac{1}{2} O_{2} (g) ⟶ C O_{2} (g); Δ H^{o} = - 282.98 k J / m o l

Calculate standard heats of formation of

F e O (s)

and

{F e}_{2} O_{3} (s)

Q. Calculate, the

Δ H

85^{o} C

for the reaction:

{F e}_{2} O_{3} (s) + 3 H_{2} ⟶ 2 F e (s) + 3 H_{2} O (l)

The data are:

Δ H_{298}^{o} = - 33.29 k J / m o l

and

Substance	${F e}_{2} O_{3} (s)$	$F e (s)$	$H_{2} O (l)$	$H_{2} (g)$
$C_{P}^{o} (J / K m o l)$	$103.8$	$25.1$	$75.3$	$28.8$

Q. The standard enthalpies of formation of

A l_{2} O_{3}

and

C a O

are

- 1675 k J m o l^{- 1}

and

- 635 k J m o l^{- 1}

respectively.
For the reaction,

3 C a O + 2 A l \to 3 C a + A l_{2} O_{3}

the standard reaction enthalpy,

Δ_{r} H^{0}

=______kJ (Rounded off to the Nearest Integer).

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Calculate ΔfHo (in kJ/mol) for Cr2O3 from the ΔrGo and the So values provided at 27oC.4Cr(s)+3O2(g)⟶2Cr2O3(s) ;ΔrGo=−2093.4kJ/mol; So(J/Kmol):So(Cr,s)=24; So(O2,g)=205; So(Cr2O3,s)=81

The correct option is D −1129.05kJ/molAs we know,ΔG=ΔH−TΔS;ΔH=ΔG+TΔS=−2093.42+3002×1000×(2×81−3×205−4×24)=−1129.05 kJ/mol

The correct option is D $- 1129.05 k J / m o l$
As we know,
$Δ G = Δ H - T Δ S;$

$Δ H = Δ G + T Δ S = - \frac{2093.4}{2} + \frac{300}{2 \times 1000} \times (2 \times 81 - 3 \times 205 - 4 \times 24) = - 1129.05 k J / m o l$