module 5 - revision deck

Question 1

soluble ions

Answer 1

• all group 1 cations and NH4+ (no exceptions)
• Cl-, Br-, I- (except Ag, Pb, Hg)
• SO42- (except Ba, Pb, Ca, Hg)

Question 2

insoluble ions

Answer 2

• SO32-, CO32-, PO43- (except group 1 and NH4)
• S2- (except all group 1, 2, and NH4+)
• O2- (except all group 1, Ba2+ and Ca2+)
• OH- (except all group 1, NH4+, Ba2+ and Ca2+)

Question 3

cobalt chloride hydrated and dehydrated equation

Answer 3

[Co(H2O)6]2+ + 4Cl- –> CoCl42+ + 6H2O

pink –> blue

Question 4

iron(III) nitrate and potassium thiocyanate

Answer 4

Fe3+ + SCN- –> [FeSCN]2+

pale yellow, colourless –> brown/red

Question 5

open system

Answer 5

interacts with its environment, meaning that energy and matter are constantly moving between the system and the environment

Question 6

closed system

Answer 6

energy can move between the system and environment, but matter cannot

Question 7

static equilibrium

Answer 7

occurs when the forward and reverse reaction rates are both zero

Question 8

dynamic equilibrium

Answer 8

when the forward and reverse reactions are happening at the same time and the same rate

Question 9

characteristics of an equilibrium system

Answer 9

• closed system
• reversible reaction
• macroscopic properties stay constant
• concentrations of all reactants and products stay the same
• continuous changes at the atomic level
• equilibrium can be approached from either direction

Question 10

combustion reactions

Answer 10

irreversible reaction that only proceeds in one direction and goes to completion. Exothermic reaction and most occur spontaneously

Question 11

photosynthesis

Answer 11

irreversible endothermic reaction, not spontaneous. respiration looks like the reverse, but both photosynthesis and respiration go to completion and are not reversible

Question 12

activation energy

Answer 12

• the energy needed to start a chemical reaction
• many reactions go to completion because of the low activation energy
• for a reaction to be reversible, both the products and reactants need to have enough energy to react

Question 13

le châtelier’s principle

Answer 13

if a system is in equilibrium, and it is disturbed or changed in any way, then the system will adjust itself to minimise the amount of change

Question 14

interaction between nitrogen dioxide and dinitrogen tetroxide

Answer 14

2NO2(g) –> N2O4

delta H < 0

Question 15

effect of temperature on equilibrium

Answer 15

increasing temperature shifts equilibrium towards the endothermic reaction, and decreasing temperature will shift equilibrium towards the exothermic reaction

Question 16

effect of concentration on equilibrium

Answer 16

increasing the concentration of reactants will favour the reaction forming products, and increasing the concentration of products will favour the reaction forming reactants

Question 17

effect of volume/pressure on equilibrium

Answer 17

increasing pressure will shift equilibrium towards the side of the reaction with fewer moles of gas, and decreasing pressure will favour the side of the reaction with more molecules of gas.
gases must be present for pressure to have an effect

Question 18

effect of catalyst on equilibrium position

Answer 18

catalysts have no effect on equilibrium position, but the reaction will reach equilibrium faster

Question 19

Keq

Answer 19

products/reactants

Question 20

reaction quotient Q

Answer 20

if Q=Keq then system at equilibrium
Q < Keq, forward reaction favoured
Q > Keq reverse reaction favoured

Question 21

keq and equilibrium position

Answer 21

Keq > 1 indicates that equilibrium lies to the right

Keq < 1 indicates that equilibrium lies to the left

Question 22

temperature on equilibrium expression

Answer 22

exothermic: as temp increases, Keq decreases
endothermic: as temp increases, Keq increases

Question 23

dissolution of ionic compounds in water

Answer 23

solute dissolves when the energy of the bonds it forms with water are lower than the energy of the bonds between water molecules, or between the ions of the substance being dissolved

Question 24

cycad fruit equilibrium stuff

Answer 24

contains toxins cycasin and BMAA (can lead to liver disorders, disturb nerve function, and cause cancer)
toxins are water soluble - fruit is soaked
leaching (cut up fruit, place in water, leave to soak, replacing the water to allow new equilibriums to form, heated and dried)
toxins toxins

Question 25

Ksp

Answer 25

the product of the concentration of each ion in a saturated solution of a sparingly soluble salt at 298K, raised to the power of their stoichiometric coefficients
the higher the Ksp, the more soluble the salt is

Question 26

predicting the formation of precipitates using Ksp

Answer 26

if the product of the concentrations of ions > Ksp, the solution is saturated and a precipitate forms

if the product of the concentrations of ions < Ksp, the solution is unsaturated and no precipitate forms

Question 27

common ion effect

Answer 27

when two solutions are mixed and they contain a common ion, the solubility of any precipitate forming is reduced