AS physical + tests

Question 1

Test for ammonium

Answer 1

1. Add Warm NaOH
2. heat gently
3. place damp red litmus above

Result - red litmus turns blue

Question 2

Test for carbonates

Answer 2

1. Add diluted HCl (aq)
2. Collect gas produced
3. bubble through limewater

Result - limewater goes milky

Question 3

Test for sulphate

Answer 3

1. Add barium nitrate
   Result - form white p.p.

Question 4

Test for halides

Answer 4

Add silver nitrate
Result :
Chlorine - white p.p.
Bromine - cream p.p.
Iodine - yellow p.p.

Question 5

How to identify the halide test result better

Answer 5

Add diluted ammonia sol. to the p.p.
Chlorine - dissolve in dil. NH3
Bromine - dissolve in conc. NH3
Iodine - remains insoluble

Question 6

enthalpy change

Answer 6

the change in heat content of a system during a reaction

Question 7

enthalpy change of combustion

Answer 7

the enthalpy change when 1 mole of a subtance is completely combusted

Question 8

enthaply change of formation

Answer 8

the enthalpy change when 1 mol of a compound is formed from its element

Question 9

enthalpy change of neutralisation

Answer 9

the enthalpy change when 1 mol of water is formed from a neutralisation reaction

Question 10

Activation energy

Answer 10

the minimum energy required for a reaction to take place

Question 11

Average bond enthalpy

Answer 11

the energy required to break 1 mol of GASEOUS bonds

Question 12

Endothermic

Answer 12

E(Bonds breaking) > E(bond making)
takes in energy from surrounding

Question 13

Exothermic

Answer 13

E(Bond breaking) < E(bond making)
releases energy to surronding

Question 14

Standard conditions

Answer 14

100 kPa and 298K

Question 15

Hess’s law

Answer 15

the enthalpy change of a reaction is independent of the route it takes

Question 16

Bond dissociation energy

Answer 16

Amount of energy used to break 1 mol of specific covalent bond in gaeous state

Question 17

General eq for ΔHf
enthalpy change of formation

Answer 17

Elements -> compound

Question 20

Collision theory

Answer 20

the theory which states that molecules must collide with:

1. sufficient energy ( energy > Ea)
2. at the correct orientation

for a reaction to occur

Question 21

hetrogenenous catalyst

Answer 21

Catalyst in a DIFFERENT state to reactant

Question 22

Homogenenous catalyst

Answer 22

Catalyst in the SAME state to reactant

Question 23

Collision frequency

Answer 23

no. of collision per given time

Question 24

3 factors that affects rate

Answer 24

1. Temp.
   2.Conc.
   3.Pressure

Question 25

benefits of catalyst in economic terms

Answer 25

1. ↓temp and Pa needed
2. ↓ CO2 emission
3. ↓lower fuel demand
4. ↓lower economic cost

Question 26

3 methods to record rates

Answer 26

1. Volume of gas produced (/time)
2. change in mass (/time)
3. time for dissapearance/ colour change

Question 27

What are the axises for Boltzman’s distribution?

Answer 27

y - no. of particles
x- the energies

Question 28

What 3 factors have no effect on Boltzman’s districution? Why?

Answer 28

Pressure, concentration and surface area
1. It increase Frq. of successful collision
2. No effect to energies of individual molecules
3. No change to shape of curve

Question 29

Effect of temperature increase to Boltzman’s curve

Answer 29

SHIFTS RIGHT
↑ % of molecules have energies >= Ea

Question 30

Effects of Catalyst on Boltzman’s distribution

Answer 30

1. ↓ Ea
2. No affect of energies of individual molecules
3. 3. ONLY greater % of molecules with energies >= Ea

Question 31

Homogeneous equilibrium

Answer 31

An equilibrium in which all reactants are in the same state

Question 32

Dynamic equilibrium

Answer 32

A closed system in which
* rates of foward and reverse reaction are the same
* Conc. of reactant and product are constant

Question 33

Le chatellier’s principal

Answer 33

When a system in dynamic eqm is subject to change, the position of eqm will shifts to oppose the change.

Question 34

Factors that affects position of eqm

Answer 34

Temp., Pressure, Conc.

NOT catalyst as it ↓ Ea for both foward and reverse

Question 35

E.g Le Chatelier principal

Q: Effect on position of Eqm when temp increases?

Answer 35

Shifts to endothermic

Question 36

E.g Le Chatelier principal

Q: Effect on position of Eqm when pressure increases?

Answer 36

Shifts to side with ↓ gas moles

Question 37

E.g Le Chatelier principal

Q: Effect on position of Eqm when c(Product) increases?

Answer 37

Shifts to favor reactant (LHS)

Question 38

3 optimal conditions for haber process

N2+3H2 ⇌ 2NH3

Answer 38

1. ↑ pressure ( less gas moles on the right)
2. ↓ temp. (Foward reaction is exo.)
3. ↑ c( N2 + H2) and low c(NH3)

Question 39

What are the comprimise to conditions for reactions ?

Answer 39

Need to comprimise between
1. Rate + time consumption
2. Eqm - % yield
3. safety (↑Pa - dangerous)
4. cost (↑temp - ↑ cost for fuel)
5. ↓PA - Rates maybe too slow

Question 40

Indication when Kc = 1

Answer 40

conc(reactant) = conc(Product)
eqm at the centre

Question 41

Indication when Kc < 1

Answer 41

conc(reactant) > conc(Product)
eqm to LHS

Question 42

Indication when Kc >1

Answer 42

conc(reactant) < conc(Product)
eqm to PHS