Question

The value of $\Delta H$ for cooling $2$ mole of an ideal monoatomic gas from $225^{\circ} C$ to $125^{\circ} C$ at constant pressure will be [given $\left.C_{p}=\frac{5}{2} R\right]$

• A. 250 R
• B. -500 R
• C. 500 R
• D. -250 R

Answer 1

Answer: (B)

$\Delta H=-n C_{p} \Delta T$
$=-2 \times \frac{5}{2} R(225-125)$
$=-5 R(100)=-500\, R$