Unit 6 - Solubility and Chemical Equilbrium

Question 1

Water

Answer 1

polar molecule;
very high boiling point due to hydrogen bonding;
solid phase is less dense than liquid phase;
ability to dissolve a variety of solutes;
can form hydration shells;
amphoteric

Question 2

Electrolytes

Answer 2

solutes that produce ions that act as carriers of electrical charge in solution

Question 3

Electrolyte strength

Answer 3

strong = dissolves completely into ions in water;
weak = only a small amount of ions are released;
non-electrolyte = molecules don’t break into ions at all;
strength is also determined based on number of ions produced

Question 4

Total vs. net ionic equations

Answer 4

total ionic equation = shows dissociation of all products and reactants;
net ionic equation = removes spectator ions from equation

Question 5

Activity

Answer 5

expressed as the product of the activity coefficient and the ratio of the stoichiometric concentration or pressure to that of a reference state;
activity = 1 for solids and liquids

Question 6

Prediction reaction direction

Answer 6

Q = 0 - pure reactants;
Q < K - forward reaction;
Q = K - equilibrium;
Q > K - reverse reaction;
Q = infinity - pure products

Question 7

Le Châtelier’s principle

Answer 7

increasing temperature favours endothermic reaction;
increasing pressure favours reaction with least number of moles;
adding an inert gas would have no effect;
catalysts make the reaction proceed faster, but in both directions

Question 8

Solubility and precipitation

Answer 8

Ksp depends on temperature and pH;
to determine K for a precipitation reaction, it is the inverse of Ksp;
Q < Ksp = no precipitate;
Q > Ksp = precipitate

Question 9

Diesel engines and smog

Answer 9

NOx gases are continually being produced by diesel engines due to lean fuels (low fuel to air ratio);
the increase in NO2 offsets the N2O4 and NO2 equilibrium, causing increased smog;
at cold temperatures it’s clear, at warm temperatures it’s brown

Question 10

Defluoridation

Answer 10

ion-exchange process uses charred animal bone that is filtered for defluoridation via fluoride ion adsorption;
due to ion exchange mechanism

Question 11

Pesticides and organic pollutants

Answer 11

organic pollutants (pesticides, drugs) are persistent (resist chemical transformation), toxic (acute or chronic) and bioaccumulate (build up in fatty tissue);
due to high Kow, high lipophilicity leads to slow metabolism

Question 12

Nitrogen fixation

Answer 12

nitrogen fixation has led to better fertilizers which increases yield of crops;
this allows for a greater population;
however, ammonium nitrate is also a main component of explosives