Question

-TRUE or FALSE? ( If the statement is false, briefly state why the statement is false)

Part A- when a soluble solute is dissolved in a solvent, the boiling point of the solvent will decrease.?

Part B- As the coordination number of a unit cell increases, the overall packing efficiency of atoms decreases?

Part C - When a solid dissolves into water and the container feels cold to the touch, the heat of hydration is greater than the combined lattice energy of the solid and the heat of solvent?

Part D - Hydrogen-bonding interactions will dominate intermolecular interactions at a greater distance of seperation than ion-dipole interactions?

Answer 1

Part A : when a soluble solute is dissolved in a solvent, the boiling point of the solvent will decrease?

The answer for this question is that it is a true statement.

For any solvent, the presence of spolute in it decreases its vapour pressure. Boiling point is defined as boiling of a liquid starts at its surrounding atmospheric temperature. Hence when the solute is added,more temperature is to be provided to boil the given solution.

Part B- As the coordination number of a unit cell increases, the overall packing efficiency of atoms decreases?

The above statement is False one.

Now the answer to this question is that, the coordination no. of unit cell and its packing efficiency are directly proportional i.e. both increases.

Explanation to this is that the arrangement of particles can be 1D, 2D or 3D. When we have 2D or 3D arrangengement, each lattice point is surrounded by certain no. of other spheres, this is its coordination number. For example, the coordination no. of simple lattice is 6 and its packing efficiency is 52%. Similarly the coordination no. of body centered lattice type is 8 and its packing efficiency is 68% and for Face-centered lattice type the coordination no. is 12 and its packing efficiency is 72%.

Part C - When a solid dissolves into water and the container feels cold to the touch, the heat of hydration is greater than the combined lattice energy of the solid and the heat of solvent?

The answer to the above given question is that it is a False statement.

First one should know the defination of heat of hyderation to explain this answer. It goes as "The heat of hydration is the heat emitted when 1 mol of gaseous solute ions is dissolved in water".

Hence, when on touching the container one feels cold to touch means that the reaction is endothermic i.e. the reaction needs energy from outside to proceed the reaction. When I delta

then the amount of energy required to seperate solute into its constituent ions is greater than the energy given off when the ions are hydrated. Is therefore positive and the solution process is endothermic.

Part D - Hydrogen-bonding interactions will dominate intermolecular interactions at a greater distance of seperation than ion-dipole interactions?

An ion-dipole force consists of an ion and a polar molecule interacting. They align so that the positive and negative groups are next to one another, allowing maximum attraction. Hence ion-dipole interaction is stonger than the H-bonding.

Hence the above statement is True as the H-bonding will dominate intermolecular interactions at a greater distance of seperation than ion-dipole interactions.

As the H-bonding is weaker than ion-dipole interaction it will have intermolecular interactions at a greater distance of seperation than ion-dipole interactions.