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JEE Advanced · Physics · 13. Thermodynamics

Two moles of ideal helium gas are in a rubber balloon at \(30^{\circ} \mathrm{C}\). The balloon is fully expandable and can be assumed to require no energy in its expansion. The temperature of the gas in the balloon is slowly changed to \(35^{\circ} \mathrm{C}\). The amount of heat required in raising the temperature is nearly (take \(R=8.31 \mathrm{~J} / \mathrm{mol} . \mathrm{K}\) )

  1. A \(62 \mathrm{~J}\)
  2. B \(104 \mathrm{~J}\)
  3. C \(124 \mathrm{~J}\)
  4. D \(208 \mathrm{~J}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(208 \mathrm{~J}\)

Step-by-step Solution

Detailed explanation

The heat is supplied at constant pressure. i.e., the process is isobaric

\(\begin{array}{l}

\therefore Q=n C_{p} \Delta t \\

=2\left[\frac{5}{2} R\right] \times \Delta t=2 \times \frac{5}{2} \times 8.31 \times 5=208 \mathrm{~J} \\

\left(\because C_{p}=\frac{5}{2} R \text { for mono-atomic gas }\right)

\end{array}\)
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