CHEM ATP

Question 1

(c) Give two observations that are made as the silver chloride breaks down. electro

Answer 1

• yellow / green gas
• bubbles / effervescence
• shiny liquid / metal / solid / deposit / substance

Question 2

why repeat

Answer 2

can spot anomalous results
OR
can find a mean/average

random- don’t forget excess hcl for acid and metal or carbonate

Question 3

Explain why the bung must be replaced immediately after the sodium carbonate is added to the boiling tube.

(ii) Explain how the apparatus could be altered so that the bung does not have to be removed.
You may draw a diagram to explain your answer.

Answer 3

gas escapes before bung is replaced /so that gas does not escape

place one reagent in tube inside boiling tube / flask
* tip / shake tube to start reaction OR
* use a divided flask
* tip flask to start reaction- (The reaction can be started by tipping the flask
* do not have to replace / remove the bung
* so no gas escapes (while the bung is being removed / replaced )

Question 4

hydrated copper(II) sulfate in a boiling tube and heated using a Bunsen burner.

Answer 4

• white fumes given off
• condensation at mouth of tube
• solid (changes from blue and) becomes white

Question 5

temperature decrease

Explain why the temperature decrease becomes constant for high masses of sodium
hydrogencarbonate.

Suggest two changes that could be made to the apparatus that would improve the accurate results

Answer 5

all) acid used up / sodium hydrogen carbonate in excess- reaction over

use a pipette- more accurate than a measuring cylinder

use a polystyrene / styrofoam cup -insulator / reduces heat gain

ror gas- use a divided flask

Question 6

safety precaution

Answer 6

safety glasses/goggles/gloves/lab coat

Question 7

A few drops of liquid P were placed in a crucible. A lighted splint was applied to the surface of liquid P in the crucible- burned with an orange flame and lots of smoke;
soot was left around the top of the crucible

A few drops of liquid P were added to a test-tube containing 1cm3
of aqueous bromine.- colour changed from orange to colourless

Answer 7

flammable / fuel unsaturated / alkene / any named alkene organic / contains carbon / hydrocarbon

Question 8

Describe what would happen if the apparatus is used before the error is corrected- conical flask and both tubes inside

Answer 8

liquid / drying-agent pushed out of flask

Question 9

Explain why the graph line must pass through (0,0).

• bunsen burner adjust to give hot flame

Answer 9

there is no reaction (with no magnesium)

Open (air hole / collar)

Question 10

Suggest a practical problem that using 50cm3
of solution C could cause. How could this
problem be solved?

Answer 10

Volume of potassium manganate solution added > 50 cm3
Use more than one burette / refill burette

Question 11

suction pump

Answer 11

suck gases/ products formed. through apparatus

Question 12

The student calculated that the total volume of gas collected in this reaction would be 85cm3
.
Suggest and explain why the actual volume of gas collected was different from 85cm3

Answer 12

volume of gas would be lower, gas dissolved in water

Question 12

titration- what readings to take

Answer 12

initial burette reading and final burette reading

Question 13

After the titration, the student discarded the contents of the conical flask and rinsed the conical flask with distilled water.
Suggest and explain what would be the effect, if any, on the titration values if the conical flask was not dried before repeating the titration.

Answer 13

values should be same moles / amount of sodium hydroxide added still same

Question 14

ui not used in titration

Answer 14

too many colour changes no clear end point

Question 15

determining concentration of acid which is highest

Answer 15

thermometric
* measure temperature (change)
* highest temperature (change) is most concentrated
* add (xs) hydrochloric acid

precipitation of metallic hydroxide
* measure mass / height of precipitate
* most precipitate is most concentrated
* add (xs aqueous) copper sulfate (for example)

gas produced
* measure volume of gas made
* largest volume is most concentrated
* add an ammonium salt or aluminium

evaporation
* mass of solid
* most mass is most concentrated
* evaporate solution

pH meter
* measure pH
* highest pH is most concentrated
* pH meter

dissolving
* measure time taken for solid to dissolve
* shortest time is most concentrated
* aluminium / aluminium oxide / zinc / zinc oxide

Question 16

A lighted splint was used to touch about 1cm3
of liquid V.
liquid V set on fire and
burned with a smoky blue flame- pleasant smell-
(e) Draw one conclusion about liquid V.

Answer 16

fuel/ organic

Question 17

chromatography place dot apparatus

Answer 17

teat pipette or dropper

Question 18

Suggest what might have caused this result to be anomalous.- titration

Answer 18

overshot end point / more than 25 cm3 KOH in flask

Question 19

cotton wool purpose

Answer 19

allow gas to escape Prevent loss of acid;

Question 19

What conclusion can you draw about the identity of solid O from test 1?- white crystal

Answer 19

group 1 cation present

Question 19

Suggest a practical problem that using 50 cm3 of solution C in this investigation would cause. Suggest a practical solution to the problem

Answer 19

volume of potassium manganate(VII) solution added would be greater than 50 cm3 solution: use more than one burette / refill burette

Question 20

thermometer not in alcohol

Answer 20

to measure the temperature of vapour/ temperature of liquid would not be constant