Question

A) a container is half filled with a liquid and sealed at room temperature and atmospheric pressure. what happens?
b) NaCl crystallizes in a cubic unit cell with Cl- ions on each corner and each face and Na+ ions on each edge (12) and one inside. how many Na+ and Cl- ions are in each unit cell?
c) the energy absorbed when dry ice (co2) sublimely is required to overcome which type of interaction

Answer 1

A) Evaporation continues until it and the rate of condensation become equal. This is known as the equilibrium vapor pressure. At that point, and with no other changes to the system, the internal pressure will become a constant value. The two processes (evap and cond) will continue but in equilibrium (i.e. balancing out).

B) no. Of corner in unit cell : 8 , contribution by each corner : 1/8

No. Of face in unit cell : 6 , contribution by each face : 1/2

No. Of Cl- ions in unit cell = 8 × 1/8 + 6 × 1/2 = 4

no. Of edge in unit cell : 12 , contribution by each edge : 1/4

No. Of Na+ ions in unit cell = 12 × 1/4 = 3

C) Dry ice is the solid form of carbon dioxide (CO2). Carbon dioxide is a linear molecule composed of a carbon atom at the center and two oxygen atoms at the ends. The carbon is double bonded to both oxygen atoms. As a result, carbon dioxide has no net dipole moment, meaning it is a non polar compound. It cannot form any charged interactions or hydrogen bonds with itself, so the only intermolecular forces it can exert are Van der Waals forces.This Van der Waals force is also known as london dispersion force.

The energy absorbed when dry ice (co2) sublimely is required to overcome London dispersion force.