We can use Graham's law of diffusion to solve this problem, which states that the rate of diffusion of a gas is inversely proportional to the square root of its density.
Let's first find the rate of diffusion of oxygen and chlorine:
Rate of diffusion of oxygen = Volume of oxygen / Time taken = 60 cm3 / 10 s = 6 cm3/s
Rate of diffusion of chlorine = Volume of chlorine / Time taken = 100 cm3 / 30 s = 3.33 cm3/s
Now, we can set up the following equation using Graham's law:
Rate of diffusion of oxygen / Rate of diffusion of chlorine = sqrt(density of chlorine / density of oxygen)
Plugging in the values we have calculated, we get:
6 cm3/s / 3.33 cm3/s = sqrt(density of chlorine / 1.25)
Simplifying and solving for density of chlorine, we get:
Density of chlorine = (6 cm3/s / 3.33 cm3/s)2 * 1.25 = 5.67 g/cm3
Therefore, the density of chlorine is approximately 5.67 g/cm3.