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JEE Main levelSingle correct optionDifficulty 2 of 3td125

Two moles of an ideal diatomic gas ( $C_{V} = \frac{5}{2} R$ ) are heated at constant pressure from $300 K$ to $350 K$ . With $R = 8.314 J mo l^{- 1} K^{- 1}$ , the enthalpy change $Δ H$ is closest to

A $2078 J$
B $831 J$
C $2910 J$
D $1455 J$

Answer: C

Δ H = n C_{P} Δ T

with

C_{P} = C_{V} + R = \frac{7}{2} R

.

Δ H = 2 \times 3.5 \times 8.314 \times 50 = 2910 J

. The value

2078 J

is

Δ U

(

C_{V}

used),

831 J

is

n R Δ T

and

1455 J

omits

n

.

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