Practice Questions

Question 1

A white solid was thought to be barium carbonate. A student suggested that the presence of
the carbonate ion could be tested for by adding a small amount of sulfuric acid.why is this wrong

Answer 1

Because usually to test for carbonate ions we add acid so that co2 will be produced however in this case barium sulfate would be produce which is very insoluble and may cause it to appear that the carbonate is not reacting

Question 2

Explain how the trend in reactivity for group 2 elements is determined by their electron configuration

Answer 2

Outer electrons is further from nucleus
There is more shielding from shells of inner electrons
So it takes less energy to remove electron so reactivity increases down group(first ionisation energy decreases down group)

Question 3

The solution of X was dissolved in deionized water, acidified with HCl, and then barium chloride (BaCl₂) solution was added.
A white precipitate formed, indicating the presence of..

Answer 3

Sulfate ions as barium chloride will only form white precipitate if sulfate ions are present

Question 4

Why might the experimental volume be Dif from theoretical volume assuming no gas escaped and measurements are made accurately

Answer 4

Incomplete reaction

Question 5

During flame test why do we dip nichrome into hcl

Answer 5

To remove residue if any other previous sample

Question 6

Explain the trend in thermal stability of group two nitrates down the group

Answer 6

Become more stable down group as atomic radius increases less polarising effect on carbonate ions so o-n bond less weak

Question 7

Aqueous sodium carbonate and aqueous sodium sulfate are both colourless solutions.
Give the reagent and the observation to show the presence of carbonate ions.

Answer 7

Strong acid , we get effluence and fizzing

Question 8

Some plastic products can be cleaned and used again.
Give two other uses of waste plastic.

Answer 8

Recycled
Incrinated for energy
Used as a feedstock for cracking

Question 10

Explain the two major reasons for cracking hydrocarbons.

Answer 10

Shorter chain alkanes and alkenes formed
Shorter chain alkanes more flammable so can be used as fuel
Shorter chain alkenes can be used to make plastics
They are higher in demand so have more value

Question 11

Describe the stages by which the reaction of NO+CO to form c02 and n2 occurs in a catalytic converter.

Answer 11

Absorption of gases on catalytic surface
Weakening of bonds on catalytic surface
De absorption of products from catalytic surface

Question 13

Explain what is meant by stereoisomers

Answer 13

Compounds that have the same structural formula but the atoms are arranged differently in space

Question 14

What type of steriosomerism is cis and trans ,e/z

Answer 14

Geometric -same structural formula but different arrangement of atoms in space (same definition as steriosomerism )happens due to restricted rotation around pi bond

Question 15

What is a condition that we need to form a carboxylic acid when oxidising an alcohol that we don’t need when oxidising to aldehyde

Answer 15

Heat under reflux for carboyxlic acid
For aldehyde we just gently distil it out as it forms

Question 16

What does potassium dichromate reduce to in oxidising an alcohol

Answer 16

It reduces to GREEN (from orange )

Question 17

Why might yield not be 100 percent

Answer 17

Loss on transfer
Side reactions
Incomplete reactions

Question 19

Booing temp of substances is 51 what is a suitable range to collect this substance

Answer 19

50-52
Do one degree before and one after

Question 20

Correct set up for distillation

Answer 20

Thermometer should be in vapour not the liquid
Add anti-bumping granules before heating:
Promotes smooth boiling → improves yield and purity.
Water should enter condenser from the bottom and exit from the top:
Maximises cooling efficiency → improves yield by full condensation.
Leave the receiving flask open to the atmosphere:
Prevents pressure buildup → safer and improves yield.
Use clamps/stands to support all glassware securely:
Prevents apparatus movement → ensures consistent yield and avoids accidents.
Ice-water bath under the receiving flask (optional):
Helps condense low-boiling distillates → improves yield and purity.

Question 21

Why might there be no molecular ion peak

Answer 21

Molecule fragments /molecular ion is unstable

Question 22

When alcohol X is oxidised, a carboxylic acid is formed.
State what information this gives about alcohol X.

Answer 22

Its primary
If it just formed an aldehyde its still primary but incomplete oxidation
Secondary alcohols forms ketones only partial oxidation no carboxylic acid
Tertiary -no reaction

Question 23

Give the reason why sodium hydrogencarbonate solution is added to the organic layer
why it is important to open the tap after adding this solution.

Answer 23

To neutralise any acid
To release c02 to prevent pressure building up

Question 24

Reflux apparatus

Answer 24

Water flow in at bottom out at top
Heat source at bottom of flask
No stopper on condenser as build up of pressure
No gap between condenser and flask as gas leaves
Condenser must be vertical not slanted as that’s for distillation
Anti bumping granules

Question 25

Why do we need drying agent in purification

Answer 25

Absorbs water to remove it

Question 26

How do anti bumping granules prevent bumping

Answer 26

They allow heat to be disturbed evenly

Question 27

What is the point of reflux

Answer 27

To heat reaction without loosing volatile product as product will condense back in to pear shaped flask

Question 28

Describe how the student should prepare the 250.0 cm3 of ethanedioic acid solution

Answer 28

Weight out known mass use balance of ethanedioic acid transfer to volumetric flask using funnels use distilled water to rinse funnel and weighing boat and add the water to flask, fill flask to 250cm cubed point

Question 29

State the uses or barium sulfate and how its safe

Answer 29

Used to absorb X-rays Insoluble so no toxic ba2+ ions released to body

Question 30

Solutions of barium hydroxides are used in titration of weak acids Why is magnesium hydroxides not used

Answer 30

Mg(oh)2 is not very soluble so will not be able to produce enough of a concentrated alkaline solution to neutralise the acid

Question 31

Why should water not be used to put out a fire that has magnesium burning

Answer 31

H2 is flammable explosive reaction would occur

Question 32

Why does silicon have a specifically high boiling point

Answer 32

It’s macromolecular a lot of heat energy required to break strong covalent blond

Question 33

Explain trend of melt point down group 2

Answer 33

(Not same as thermal stability) Decreases as atomic radius increases so weaker attraction for delocalised electrons weaker metallic bonds

Question 34

Why is gas syringe more accurate than collecting gas over water

Answer 34

Prevents loss of gas during setup

Question 35

Activation energy is

Answer 35

The minimum energy required for a reaction to take place when a reactant molecules collide

Question 36

If experiment includes hydrogen what are the risks

Answer 36

Hydrogen is flammable

Question 37

Give a reason why the catalyst is warmed and a reason why the catalyst may melt.

Answer 37

Temperature rise gives faster rate to provide the activation energy Heat given out was exothermic enough to break bonds in copper

Question 38

Describe the processes that occur on the surface of a heterogeneous catalyst during the oxidation of ammonia in air.

Answer 38

Reactants absorb on to catalyst surface Bonds in reactants are weakened Products deabsorb from catalyst surface

Question 39

If the forward reaction is exothermic what happens to kc if temperature increases

Answer 39

Kc decreases due to forwards exothermic reaction

Question 40

Describe how you would find a numerical value for the initial rate of reaction and for the maximum rate of reaction in this experiment from the graph. No actual calculations are required.

Answer 40

Tangent at t=0 for the intial rates For the max rate take tangent at steepest part of curve Find gradient by change in concentration/time

Question 41

What goes on y and x axis of maxwell distrubution curve

Answer 41

Y-particles with energy X-energy

Question 42

Explain, in terms of collisions and energy, why lowering the temperature decreases the rate of reaction.

Answer 42

Particles have less kinetic energy so less frequent collisions less molecules collisions have energy equal to or more than activation energy

Question 43

Explain, in terms of collisions and energy, why lowering the temperature decreases the rate of reaction.

Answer 43

Particles have less kinetic energy so less frequent collisions less molecules collisions have energy equal to or more than activation energy

Question 44

Explain the effect, if any, of an increase in pressure on the rate of reaction (2)

Answer 44

Will increase the rate as there are more particles per unit volume so increase in frequency of collisions between reacting molecules

Question 45

The platinum-rhodium catalyst used in this reaction is a heterogeneous catalyst. State what is meant by the term 'heterogeneous' and why a catalyst has no effect on the yield of the products in the reaction.

Answer 45

Heterogenous catalyst is the fact that its physical state will be dif to the state of the reactants Catalysts increases rate of forwards and backwards reaction

Question 46

Explain why the honeycomb structure is used in a car exhaust system.

Answer 46

Large SA allows gases to flow through the exhaust

Question 47

Explain why the honeycomb structure is used in a car exhaust system.

Answer 47

Large SA allows gases to flow through the exhaust

Question 48

Why would percentage uncertainty be dif for 2 students using same balance to get masses

Answer 48

If the student weighed a lower mass percentage uncertainty would be higher to the other students if they were weighing a higher mass

Question 49

State why a solid (heterogeneous) catalyst is suitable for a reaction in the gas phase.

Answer 49

Provides SA for the reaction

Question 50

Give a reason why the measurement of the initial rate of reaction is likely to be less accurate than the measurement of the maximum rate

Answer 50

Difficult to draw where tangent should be drawn for initial rate compared to other points on the graph

Question 51

Identify, by name or formula, the reagent(s) needed to convert propan‑1‑ol into 1‑iodopropane.

Answer 51

Red phosphorus and iodine

Question 52

For empirical formulae do the small numbers matter for moles

Answer 52

Yes the small numbers tell use the moles ratio Ch3 One moles of carbon 3 moles of hydrogen 1 to 3 ratio

Question 53

Ethanal, CH3CHO, and ethanoic acid, CH3COOH, are both soluble in water but ethanoic acid has a much higher boiling temperature than ethanal. Explain these physical properties of ethanal and ethanoic acid in terms of intermolecular forces

Answer 53

Ethanal and ethanoic acid form hydrogen bonds with water so are soluble (must be polar and form hydrogen bonds to be soluble ) Ethanoic acid has intermolecular hydrogen bonding whereas ethanal only has London forces and perm dipole interactions more energy is required to overcome hydrogen bonding