Page 74 - SP015 Past Years PSPM Chapter 6 -14 Ver 2020

PHYSICS PSPM SEM 1 1999 - 2017

PSPM 2002/2003 SF017/2 No. 14(c)(i), (ii), (iv)

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16. Two moles of helium gas is at the temperature 27 C and filled a volume of 0.02 m
initially. The helium gas expands at constant pressure until its volume becomes two
times greater. Then it expands adiabatically until its temperature returns to its initial
value which is 27 C.

(a) Sketch a graph of p versus V for both the processes. [2 m]

(b) Calculate the temperature of helium gas at the end of the expansion process at
constant pressure. [2 m]
(c) Calculate the total work done by the helium gas in the expansion process at
constant pressure. [3 m]

PSPM 2003/2004 SF017/2 No. 14(c)(ii)

17. A monoatomic ideal gas at pressure p and volume V is compressed isothermally until its
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3
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new pressure is 3p. If p and V for the gas are 1.2  10 Pa and 1  10 m respectively,
calculate the work done on the gas during isothermal compression. [3 m]

PSPM 2005/2006 SF017/2 No. 14(a), (b), (d)

18. Two identical containers X and Y has movable piston to allow gas expansion. Both
containers contain nitrogen at 30 C. Gas in container X expands adiabatically while
gas in container Y expands isothermally to twice their original volumes. Molecular
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mass of nitrogen is 28 g mol . Assume nitrogen behaves like an ideal gas.

(a) State the difference in the speed of the piston in containers X and Y during
expansion. [2 m]

(b) Using the same axes, sketch and label the p-V graphs of the expansion
experienced by the gas in containers X and Y. Assume that the initial state of the
process is p 1, V 1, and T 1. [3 m]

(c) If container Y contains 0.03 mol of nitrogen gas, calculate the work done during
the expansion. [2 m]

PSPM 2007/2008 SF017/2 No. 14(b)

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19. A 0.5 mole of ideal gas is filled in a 0.5 m container at 30 C. The gas is isothermally
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compressed to a volume of 0.3 m . Then the gas expands isobarically to its original
volume.
(a) Sketch a p-V diagram of these two thermodynamic processes. [3 m]
(b) Calculate the total work done in the processes. [10 m]

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