Enthalpies of Solution

Question 1

what two things happen when an ionic lattice dissolves in water?

Answer 1

-the bonds between the ions break to give gaseous ions (endo)
-bonds between the ions and the water are made.(exo)

Question 2

what are the factors affecting the enthalpy of hydration?

Answer 2

ionic radius:
smaller ions have a greater enthalpy of hydration. this is due to the smaller ions having a higher charge density than bigger ions. they attract the water molecules better and have more of an exothermic enthalpy of hydration.

ionic charge:
ions with a greater charge have a greater enthalpy of hydration. this is because ions with a higher charge are better at attracting water molecules than those with lower charges. more energy is released when the bonds are made, giving them a more exothermic enthalpy of hydration.

Question 3

What is entropy?

Answer 3

tells you how much disorder there is. a measure of all the ways that particles can be arranged and the number of ways that the energy can be shared between the particles (the measure of the dispersal of energy in a system.) represented by the symbol S.

Question 4

factors affecting entropy: physical state.

Answer 4

solid particles just wobble around a fixed point- there’s hardly any disorder, so have the lowest entropy. gas particles whizz around wherever they like and so have the most disordered arrangement, and so have the highest entropy.

Question 5

factors affecting entropy: dissolution

Answer 5

dissolving a solid also increases entropy- dissolved particles can move freely as they’re no longer held in place.

Question 6

factors affecting entropy: number of gaseous particles.

Answer 6

the more gaseous particle means more entropy as there are more ways they and their energy can be arranged.

Question 7

how do you calculate entropy changes?

Answer 7

entropy change= Sproducts - Sreactants