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Gas Law and Experiment 3

ACTSCI-6RJHRZ

A new compound is discovered and a chemistry student undertakes a project to study its behavior when it is heated.

Setup

He places 2 grams of this compound in a container fitted with a piston. The piston is exposed to the atmosphere and thus the contents of the container will experience a constant pressure at all times. The walls of the container encase a heating filament, the rate of heat supplied by which can be changed.

Experiment 1

Constant heat was supplied at 500 watts to 2 grams of the compound and the rise in temperature was plotted against time.

Figure 1

Experiment 2

Constant heat was supplied at 1000 watts to 2 grams of the compound and the rise in temperature was plotted against time.

Figure 2

Note: In the figures, B and D are the melting and the boiling points respectively.

The student then conducted the experiment at various heating rates. He then plotted the times required to reach the melting and boiling points against the rate of heating of the compound.

Figure 3

Experiment 3

When the compound was completely converted into gas, the student measured the change in volume with increase in temperature. He plotted the volume of the gas against the temperature of the gas and obtained the following graph.

Figure 4

The gas law states that $PV = nRT$, where $P$ is pressure, $V$ is volume, n is the number of moles of the gas, $R$ is the gas constant and T is the temperature.

Which of the following statements is correct with respect to the gas law and the information given in experiment 3?

A

A statement cannot be made regarding the relation between the temperature and the volume of the gas because variation in pressure has also to be accounted for.

B

When the temperature is zero, the volume will be zero. Therefore, the graph must originate at zero.

C

Gas constant is a function of temperature and the change in it has to be taken into account.

D

Volume is directly proportional to the temperature because P, n and R do not vary in this experiment.