QJEEM20Che26b: JEE Main 2020 Chemistry - Class 11 JEEM20Che26b Solution: The internal energy change (in J) When 90 g of water undergoes…

Question

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The internal energy change (in J) When 90 g of water undergoes complete evaporation at 100^oC is ____________.

(Given :

Δ

H_vap for water at 373 K = 41 kJ/mol,
R = 8.314 JK^–1 mol^–1)

Accepted Answer

H₂O(l) ⇌ H₂O(g)

90 gm of H₂O =

\frac{90}{18}

moles of H₂O = 5 moles of H₂O

Δ

H_vap =

Δ

U +

Δ

n_gRT

\Rightarrow

Δ

U =

Δ

H_vap -

Δ

n_gRT

= 41000 - 1

\times

8.314

\times

373

= 37898.878

For 5 moles,

Δ

U = 37898.878

\times

5 = 189494.39 Joule

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