The graph drawn with absolute temperature T on X-axis and pressure of an ideal gas P on Y-axis is as shown. As the temperature of the gas increases, the volume

PV = nTR. This gives V = nTR/P. As the graph is not passing through the origin and has positive slope (a) and negative intercept on Y-axis (-b), its equation can be written as P = aT - b. Substitution gives V=nTRaT−b=nRa−(b/T). As T increases the denominator increases and hence V decreases