Year 13 Entropy

Explain why the entropy of the system increases when sodium chloride dissolves in water. (2)

In the solid / lattice, the ions are (1) But in the solution the ions are /more dispersed / more spread out/ more random (so entropy has increased) (1)

(Dissolving results in) an increase in the number of moles of particles and from to / NaCl → Na+ + Cl−

(1) The bonds between the water molecules are disrupted

(High) positive value is expected because:

moles → moles.

(two) → and/or liquid (+ one solid)

Entropy of the surroundings for an endothermic reaction is (1)

The reaction is feasible with the total entropy being (so entropy of the system has to be a large enough positive value for this to be true).

(iii) Give two reasons why the positive sign of your answer to (a)(ii) is as you would expect.

more moles of than (3 moles → 13 moles)

Two solids in the → a gas / a liquid (+ 1 solid) in the

∆S^ɵ becomes less negative (smaller in MAGNITUDE (because you are dividing −∆H by a larger T)

∆S^ɵ / ∆H are not (significantly) affected by a change in temperature.

∆S^ɵ increases

Barium hydroxide will (very) soluble / will be sparingly soluble

and K value suggests that the equilibrium lies to the side / reactants

OR K << 1 so predominant

M1: Hydroxides get soluble as you descend Group 2 (1)

M2: ∆S^ɵ _total gets negative as you go from Ca(OH)₂ to Ba(OH)₂

and solid react to to form

There are fewer ways of arranging particles in a than a .

mol(es) of reactant forming mole of product.

mol(es) of products than reactants

Give the formula to be used

= +

Decrease in T: is not (significantly) changed.

or (−∆H/T) is more positive.

makes more positive