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Standard XII

Chemistry

Enthalpy

If Δ U of com...

Question

If $Δ U$ of combustion of $C H_{4} (g)$ ,
$C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l)$
at certain temperature is $- 393 k J m o l^{- 1}$ . The value of $Δ H$ is:

zero

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< Δ U

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> Δ U

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equal to

Δ U

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Solution

The correct option is B $< Δ U$
The reaction is
$C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l)$
$Δ n_{g} = (n_{p} - n_{r})_{g} = 1 - 3 = - 2$
and
$Δ H = Δ U + Δ n_{g} R T$
As, $Δ n_{g} = - 2$
so,
$\Rightarrow Δ H < Δ U$

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Similar questions

Q. If

Δ U

of combustion of

C H_{4} (g)

C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l)

at certain temperature is

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

. The value of

Δ H

is:

∆U° of combustion of CH4 (g)at certain temperature is -393kj/ mol.Then value of ∆H° is

1)0

2)<∆U°

3)>∆U°

4)=∆U°

Q. In which of the following reactions

Δ H

is equal to

Δ U

$Δ_{f} U^{⊖}$ of formation of $C H_{4} (g)$ at certain temperature is-393 kJ $m o l^{- 1}$ . The value of $Δ_{f} H^{⊖}$ is
(a) zero
(b) $< Δ_{f} U^{⊖}$
(c) $> Δ_{f} U^{⊖}$
(d) equal to $Δ_{f} U^{⊖}$

Q. The reaction in which

△ H > △ U

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Enthalpy

Standard XII Chemistry

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If ΔU of combustion of CH4(g), CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) at certain temperature is −393 kJmol−1. The value of ΔH is:

The correct option is B <ΔU The reaction is CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) Δng=(np−nr)g=1−3=−2 and ΔH=ΔU+ΔngRT As, Δng=−2 so, ⇒ΔH<ΔU

If $Δ U$ of combustion of $C H_{4} (g)$ ,
$C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l)$
at certain temperature is $- 393 k J m o l^{- 1}$ . The value of $Δ H$ is:

The correct option is B $< Δ U$
The reaction is
$C H_{4} (g) + 2 O_{2} (g) \to C O_{2} (g) + 2 H_{2} O (l)$
$Δ n_{g} = (n_{p} - n_{r})_{g} = 1 - 3 = - 2$
and
$Δ H = Δ U + Δ n_{g} R T$
As, $Δ n_{g} = - 2$
so,
$\Rightarrow Δ H < Δ U$