Question

dela E?

Which of the following reactions would ΔΗ = ΔΕ? Multiple Choice O C(s) + O2(9) --> CO2(g) Zn+2(aq) + 2OH(aq) --> Zn(OH)2(s) C3H4(g) + 402(g) --> 3CO2(g) + 2H2O(1) CaCO3(s) --> CaO(s) + CO2(g) 2Al(s) + 6HCl(aq) --> 2AlCl3(aq) + 3H2(g)

Answer 1

Sol :-

Relationship between enthalpy change of the reaction (ΔH) and change in internal energy (ΔE) of the reaction is :

ΔH = ΔE + RT Δng ...................(1)

If Δng = 0 , then ΔH = ΔE

If Δng > 0 , then ΔH > ΔE and

If Δng < 0 , then ΔH < ΔE

Here,

R = Universal gas constant, T = Temperature and

Δng = [Sum of number of moles of gaseous products (np)] - [Sum of number of moles of gaseous reactants (nR)]

Now,

1. Given reaction is : C (s) + O2 (g) -----------------> CO2 (g)

Here, Δng = 1 - 1 = 0

Hence, ΔH = ΔE

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2. Given reaction is : Zn2+ (aq) + 2OH- (aq) -----------------> Zn(OH)2 (s)

Here, Δng cannot be dtermine

So, ΔH not equal to ΔE

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3. Given reaction is : C3H4 (g) + 4O2 (g) -----------------> 3CO2 (g) + 2H2O (l)

Here, Δng = 3 - 5 = -2

So, ΔH < ΔE

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4. Given reaction is : CaCO3 (s) -----------------> CaO (s) + CO2 (g)

Here, Δng = 1 - 0 = 1

So, ΔH > ΔE

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5. Given reaction is : 2Al (s) + 6HCl (aq) ----------------->2AlCl3 (aq) + 3H2(g)

Here, Δng = 3 - 0 = 1

So, ΔH > ΔE

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Hence, Option (a) is the correct answer.