Core Practicals Flashcards
(58 cards)
1
Q
How do you investigate the solubility of a solid in water at a specific temperature?
A
- measure 100cm3 water & heat to desired temp.
- add known masses of solute to water & stir to dissolve fully
- stop adding when no more solid dissolves
- mass added is your solubility; g/100g of water
2
Q
What does temperature mean in the practical: investigating the solubility of a solid in water at a specific temperature?
A
higher the temp, higher the solubility of a solute
particles have more kinetic energy
3
Q
What does stirring do in the practical: investigating the solubility of a solid in water at a specific temperature?
A
increases rate of solubility, but not actual solubility
4
Q
What does on/above/under the line mean in the graph of the practical: investigating the solubility of a solid in water at a specific temperature?
A
on the line - saturated
above line - supersaturated
under line - unsaturated
5
Q
How do you investigate paper chromatography using inks/food colouring?
A
- draw a straight line in pencil ( won’t dissolve in solvent) on piece of chromatography paper
- put little spot of ink on pencil line
- stand paper in large beaker, which has about 1cm depth of water in bottom, water level must be below pencil line & spots ink, otherwise the spots will dissolve in solvent
- as water approaches top of paper, remove & draw line (pencil) to show where water rose to (solvent front)
- allow to dry
- calculate Rf value
6
Q
Why should the beaker have a lid in the experiment: investigating paper chromatography using inks/food colouring?
A
so solvent & inks don’t evaporate
7
Q
How do you calculate Rf value in the experiment: investigating paper chromatography using inks/food colouring?
A
distance travelled by dye/distance travelled by solvent
8
Q
How do you do crystallisation?
A
- evaporate some water until crystals form on glass rod
- leave to crystallise
- filter
- blot dry
9
Q
How do you do the diffusion experiment?
A
- put cotton wool soaked in hydrochloric acid on 1 side of the tube, put cotton wool soaked in ammonia the other
- the molecules will diffuse from either end]
- a white ring of ammonium chloride will form closer to the hydrochloric acid because it’s heavier (higher RFM value) so takes longer to diffuse
10
Q
What happens when you increase temperature in the diffusion experiment?
A
makes ring form faster, particles have more energy & move faster (diffuse faster)
11
Q
How can you determine the formula of a metal oxide by combustion? (e.g. magnesium oxide)
A
- record mass of empty crucible & lid
- record mass of crucible, lid & magnesium
- heat magnesium strongly, lifting lid occasionally to let oxygen in to react with magnesium, magnesium will burn bright
- heat crucible to constant mass, this means mass no longer increases
- record final mass of crucible, lid and now magnesium oxide
from data you can calculate mass of magnesium & mass of oxygen added, you can then calculate empirical formula
12
Q
How can you determine the formula of a metal oxide by reduction? (e.g. coper2 oxide)
A
- record mass of empty tube
- record mass of tube & copper oxide
- attach to gas and run methane across copper oxide, should be lit at end of test tube to ensure excess is burned off, methane reduces (removes oxygen) the copper oxide to form copper
- continue until all mass of tube remains constant - all oxygen has been removed from copper
- record final mass of test tube & now copper
from data you can calculate mass of copper & oxygen removed, you can then calculate empirical formula
13
Q
How can you investigate water of crystallisation?
A
- record mass of empty crucible
- record mass of crucible & hydrated salt
- heating crucible strongly using roaring Bunsen flame
- continue to heat until mass of crucible remains constant - heat to constant mass to ensure all water has evaporated
from data you can calculate mass of water removed and mass of anhydrous salt, by calculating moles of each you can work out water of crystallisation
14
Q
What results are seen when you do thermal decomposition of copper(2) carbonate, zinc carbonate and calcium carbonate?
A
- copper(2) carbonate is green, decomposes to form black copper(2) oxide
CuCO3(s) to CuO(s) +CO2(g) - zinc carbonate is white, decomposes to form yellow zinc oxide when hot (reverts back to white when cooled)
ZnCO3(s) to ZnO(s) + CO2(g) - calcium carbonate requires very high temperatures to decompose to white
CaCO3(s) to CaO(s) + CO2(g)
15
Q
How do you investigate the electrolysis of aqueous solutions?
A
- make sure ionic compound is dissolved in water
- connect electrodes to power source
- fill test tubes with solution & place over electrodes - any gas produced will displace solution
- turn on power source
- observe & test for any gases produced
16
Q
What happens when chlorine is produced at the anode?
A
bubbles, test using damp blue litmus paper, will turn red & bleach
2Cl- to Cl2 + 2e-
17
Q
What happens when bromine is produced at the anode?
A
solution will turn orange
2Br- to Br2 + 2e-
18
Q
What happens when iodine is produced at the anode?
A
solution will turn brown
2I- to I2 + 2e-
19
Q
What happens when oxygen is produced at the anode?
A
bubbles, test using glowing splint that relights
4OH- to O2 + 4e- + 2H2O
20
Q
What happens when hydrogen is produced at the cathode?
A
bubbles
test using splint, squeaky pop
2H+ + 2e- to H2
21
Q
What happens when copper is produced at the cathode?
A
pink/brown solid deposit
Cu2+ + 2e- to Cu
22
Q
Where does reduction and oxidation happen in electrolysis?
A
oxidation - anode
reduction - cathode
23
Q
What happens in the electrolysis of NaCl (aq)?
A
- left with Na+ and OH- ions in solution at end
- forms alkali NaOH
- universal indicator turns blue
24
Q
How do you determine the approximate % by volume of oxygen in air using a metal or a non-metal?
A
- presence of oxygen & water will cause iron to rust
- by using measuring cylinder, you can see volume of air at start, then over a period of time (5-7 days) you will see it decrease
25
What is the formula for % oxygen in the experiment: determining the approximate % by volume of oxygen in air using a metal or a non-metal?
(volume lost/initial volume) x 100
26
Why won't your calculation not give you 21% in the experiment: determine the approximate % by volume of oxygen in air using a metal or a non-metal?
it needs to be left until there is no further change in volume
27
How can you determine the approximate % by volume of oxygen in air using copper & oxidising it?
1. heat copper, move air over copper using gas syringes
2. volume of air will decrease as oxygen reacts with copper (forming copper oxide)
28
How do you investigate rusting?
- fill test tube with air & water
- fill test tube with boiled water and no air (put layer of oil)
- fill test tube with air, no water, but anhydrous calcium chloride
29
What is the purpose of the anhydrous calcium chloride in the experiment: investigating rusting?
drying agent, so removes all the water
30
What will happen if salt is added to the water in the experiment: investigating rusting?
nail will form rust at a much faster rate
31
What are the solubility rules?
1. salts containing sodium, potassium & ammonium are always soluble
2. all nitrates are soluble
3. chlorides are soluble except solver chloride & lead chloride, silver iodide & lead iodide
4. sulfates are soluble except lead sulfate, barium sulfate & calcium sulfate
5. carbonates are insoluble except for those containing sodium, potassium & ammonium
6. hydroxides are insoluble except for those containing sodium, potassium & ammonium, calcium hydroxide is slightly soluble
if you make an ionic compound that isn't soluble, you form a precipitate
32
How do you prepare a sample of pure, dry hydrated copper(2) sulfate crystals starting from copper(2) oxide (making soluble salts)?
1. warm acid to speed up rate of reaction
2. add base & stir until it is in excess (no more will react) to make sure all the acid reacts
3. filter the mixture so that the excess base is removed
4. concentrate solution by boiling it until half the water evaporates & crystals form on end of glass rod DON'T BOIL ALL WATER
5. leave solution to cool & form crystals
6. filter solution again to remove all the water
7. pat crystals dry using paper towel
CuO(s) + H2SO4(aq) to CuSO4(aq) + H2O(l)
black solid blue solution
33
How do you prepare a sample of pure, dry lead(2) sulfate (making insoluble salts/precipitates)?
1. make sure both compounds are in solution (dissolved in water)
2. mix 2 solutions together in a beaker
3. use filter paper & funnel to get precipitate
4. wash precipitate with distilled water (wash off excess ions)
5. leave salt to dry on filter paper
34
How do you test for hydrogen gas?
lit splint will burn with squeaky pop
35
How do you test for oxygen gas?
glowing splint will relight
36
How do you test for carbon dioxide gas?
bubble through limewater, which turns milky
37
How do you test for ammonia gas?
turns damp red litmus paper blue
also has pungent odor
38
How do you test for chlorine gas?
turns damp blue litmus paper red before bleaching it white
39
How do you test for oxygen gas chemically?
turns white anhydrous copper sulphate into blue hydrate copper sulphate
40
How do you test for oxygen gas physically?
boils at 100C
melts at 0C
41
How do you investigate for the products of combustion?
- put candle under funnel attatched to U tube, and put U tube in ice & water bath, this will be where the water condenses
- put the end of the U tube in a test tube with limewater in, put tube from limewater test tube to water pump, this will pull any gases released through
42
What will happen to the limewater in the experiment: investigating for the products of combustion?
turns cloudy as carbon dioxide is produced
43
What will happen in the U-tube in the experiment: investigating for the products of combustion?
water produced will condense as ice bath cools
anhydrous copper sulphate in U tube will turn blue
44
What happens if the candle is too close in the experiment: investigating for the products of combustion?
black deposit can appear on funnel - from incomplete combustion
45
How do you investigate temperature changes in salts dissolving in water, neutralisation reactions & displacement reactions?
1. measure volume of sulphuric acid (in excess) into a polystyrene cup
2. cut strip of magnesium ribbon & measure its mass
3. record initial temp of acid in cup
4. add magnesium to acid in cup & stir gently with thermometer
5. record highest temp reached by solution
46
Why do you use a polystyrene cup in the experiment: investigating temperature changes in salts dissolving in water, neutralisation reactions & displacement reactions?
insulator - minimises heat loss
47
Why do you use acid in excess in the experiment: investigating temperature changes in salts dissolving in water, neutralisation reactions & displacement reactions?
so all magnesium reacts
48
What is the source of error in the experiment: investigating temperature changes in salts dissolving in water, neutralisation reactions & displacement reactions?
heat lost from experiment
49
What does endo/exothermic reaction mean?
endothermic - temp fall, positive deltaH
exothermic - temp rise, negative deltaH
50
What does q=mcdeltaT stand for
q = heat lost/gained (Joules)
m = mass of solution (Grams)
c = specific heat capacity of water (4.2)
deltaT = change in temp of solution (C)
51
How do you investigate temperature change in combustion reactions?
1. record mass of spirit burner with cap on
2. set up apparatus as shown, make gap between wick & can 5cm
3. record initial temp of water
4. light burner
5. stir water in can from time to time so it's well mixed
6. continue heating water in can until it has reached between 50-55C
7. put cap on burner to extinguish flame
8. record highest temp reached by water
9. record mass of burner (with cap)
52
What is the source of error in the experiment: investigating temperature change in combustion reactions?
heat lost from experiment & incomplete combustion
53
What is the equation for the experiment: investigating effect of changing surface area of marble chips & concentration of HCL on rate of reaction between marble chips & dilute HCL?
CaCO3 + 2HCl to CaCl2 + CO2 + H2O
54
How do you investigate effect of changing surface area of marble chips & concentration of HCL on rate of reaction between marble chips & dilute HCL?
put marble chips in beaker with HCL & put bung on top attached to gas syringe
55
What are the CVs in the experiment: investigating effect of changing surface area of marble chips on rate of reaction between marble chips & dilute HCL?
- temp
- mass of marble chips
- concentration & volume of acid
56
What are the CVs in the experiment: investigating effect of changing concentration of marble chips on rate of reaction between marble chips & dilute HCL?
- temp
- mass of marble chips
- total volume of solution
57
How do you investigate the effect of different solids on the catalytic decomposition of hydrogen peroxide solution?
1. add given volume & concentration of hydrogen peroxide to conical flask
2. use delivery tube to connect this flask to measuring cylinder upside down in water trough
3. measure specific mass of catalyst, then add catalyst to conical flask, close bung & start timer
4. measure volume of gas produced in fixed time using measuring cylinder
5. repeat experiment using different catalysts making sure volume & concentration of hydrogen peroxide & mass of catalyst is same
6. catalyst that produces required volume of oxygen in shortest time is most effective
2H2O to 2H2O +O2
58
How do you prepare a sample of an ester (e.g. ethyl ethanoate)?
1. add few drops of conc. H2SO4 (catalyst) to boiling tube
2. add 10 drops of ethanoic acid
3. add 10 drops ethanol
4. place boiling tube in beaker of water from hot kettle, heat for 5-10 mins
5. remove tube & allow to cool
6. pour over sodium carbonate solution to purify (removes acid catalyst), a layer of ester forms on top
7. should have fruity/sweet smell
