Question

The value of $\Delta H$ for cooling $2$ mole of an ideal monoatomic gas from ${225}^{o}C$ to ${125}^{o}C$ a constant pressure will be:

[Given $C_p=\frac{5}{2}R$]

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

Answer 1

The correct option is B $-500R$

$\Delta H=-n{C}_p\Delta T=-2\times \frac{5}{2}R(225-125)$

$=-5R\left(100\right)=-500R$