Chemistry · EQUILIBRIUM

In a closed, evacuated vessel containing solid iodine, violet vapour develops until the colour intensity remains constant at a given temperature. If the temperature of the vessel is subsequently kept constant and the system has attained equilibrium, which of the following is true?

1. Sublimation of solid iodine has completely ceased.
2. The mass of solid iodine must equal the mass of gaseous iodine vapour.
3. The rate of sublimation of solid iodine equals the rate of condensation of iodine vapour.
4. Molecules of solid iodine cannot exchange with molecules in the vapour phase.