Answer:
The theoretical zero volume temperature of a gas.
Step-by-step explanation:
The experimental data for effect of temperature on Volume of a gas is plotted in the graph. The graph is a straight line. It has been extrapolated where dash line meets the temperature axis. This point shows the temperature that the gas would have if it had zero volume. Experimentally, this data is not obtained but theoretically measured by extrapolating the volume versus temperature curve.
Thus, the point where blue line meets is the theoretical zero volume temperature of a gas.