Practical-related

Question 1

if we see effervescence and heat, we must….

Answer 1

test for gas

Question 2

for cation, anion and gas tests, we must…

Answer 2

copy observations from the QA table directly

Question 3

for gas tests, we must…

Answer 3

state the name of the gas

Question 4

what does it mean to write clearly what an observation refers to?

Answer 4

note whether it is a gas/precipitate/solid/solution

Question 5

an example of soluble ppt and stating what solution forms

Answer 5

blue ppt soluble in excess aqueous ammonia to form dark blue solution

Question 6

what is the evidence for conclusion?

Answer 6

state step/question number, test and observation

Question 7

what is the chemistry involved?

Answer 7

concept behind reaction, what kind of reaction and explain

e.g displacement, neutralisation, combustion

Question 8

if need to reuse apparatus, we must…

Answer 8

wash with tap water and distilled water

Question 9

how to identify precipitates?

Answer 9

cloudiness and cannot see through

Question 10

how to identify solutions?

Answer 10

can see through and has no cloudiness

Question 11

when heating solid and see water droplets at the sides of the tube?

Answer 11

water droplets observed at the side of the test tube; water of crystallisation is lost.

Question 12

when heating solid and see the solid appear at the top of the test tube?

Answer 12

solid turned into gas and condensed at the top of the tube; solid sublimed

Question 13

when solid changes colour upon being heated?

Answer 13

the colour of the solide changed from ____ to ____

Question 14

when solid turns into liquid upon heating?

Answer 14

the solid melts to form a ____ liquid

Question 15

during QA experiment, three things we must observe is:

Answer 15

1. formation of ppt
2. production of gases
3. changes in colour of soln/ppt/solid

Question 16

magnesium ribbon in acid eg

Answer 16

upon adding magnesium strips into acid, solid magnesium dissolves in acid and effervescence produced.

gas evolved ‘pops’ a lighted splint. gas is hydrogen.

Question 17

when —- is added to solution

Answer 17

upon adding —–, —- is seen.

Question 18

soln becomes cloudy and does not change when excess was added when solns mixed?

Answer 18

a —- ppt was observed, the ppt won’t dissolve in excess

Question 19

soln becomes cloudy and becomes clear after adding excess when mixing solns?

Answer 19

a — ppt was observed; the ppt dissolves in excess giving a — soln

Question 20

no change when mixing solns

Answer 20

no visible change was observed

Question 21

when writing observations, turns into (some colour)

Answer 21

(some colour) ppt is formed

Question 22

when writing observations, solid is formed, soln turns into white ppt.

Answer 22

white ppt is formed

Question 23

when writing observations, the solution is clear, becomes transparent, is white

Answer 23

solution remained colourless

Question 24

when writing observations, limewater became cloudy

Answer 24

a white ppt was observed in the limewater

Question 25

when writing observations, carbon dioxide is fomed

Answer 25

effervescence observed, the gas gave a white ppt in limewater

Question 26

when writing observations, the ppt dissolves

Answer 26

the ppt dissolves in excess to give a colourless soln.

Question 27

recording temperature

Answer 27

to nearest 0.5 degrees Celsius

Question 28

recording mass

Answer 28

to nearest 0.01g

Question 29

recording time

Answer 29

to nearest second

Question 30

recording volume in measuring cylinder

Answer 30

0 to 1 d.p.

Question 31

recording volume in pipette

Answer 31

1 d.p.

Question 32

recording volume in burette

Answer 32

to nearest 0.05 cm cube

Question 33

when drawing graph, y-axis is

Answer 33

the dependent variable (measured quantities such as time, temp., vol. of gas produced)

Question 34

when drawing graph, x-axis is

Answer 34

the independent variable (changed quantity asked by question such as conc.)

Question 35

graph requirements

Answer 35

1. Title
2. Axis titles
3. X data points
4. Larger triangle to minimise error
5. Marked big squares
6. Start labelled

Question 36

key source of error for salt preparation

Answer 36

salt may not be completely dry, loss of some salts during filtration/transfer

Question 37

key source of error for energy changes

Answer 37

heat loss to the surroundings

Question 38

key source of error for speed of reaction

Answer 38

human reaction time (with respect to use of stopwatch for e.g.)

inconsistent swirling/ stirring of solution mixture

Question 39

how does salt not being completely dry affect the results and how to improve?

Answer 39

mass of salt obtained will be greater than expected. we should dry salt between filter paper.

Question 40

how does loss of some salt during filtration/transfer affect the results and how to improve?

Answer 40

mass of salt obtained will be lower than expected. we should rinse with deionised water during filtration/transfer.

Question 41

how does heat loss to the surroundings affect the results and how to improve?

Answer 41

temp. change is less/smaller than expected; use a lid or insulate the apparatus

Question 42

how does human reaction time affect the results and how to improve?

Answer 42

inaccurate time measurements; take average of readings

Question 43

how does inconsistent swirling/stirring of solution mixture affect the results and how to improve?

Answer 43

inaccurate time measurements; use magnetic stirrer