C7 Practical Skills

Question 1

C1 Reactivity Trend

What happens if a metal reacts with a dilute acid?

Answer 1

You see bubbles of hydrogen leaving the surface od the metal.

Question 2

C1 Reactivity Trend

The faster the bubbling…?

Answer 2

The more reactive the metal is (being reacted w/ acid).

Question 3

C1 Reactivity Trend

True or False?: very reactive metals are safe to used with an acid, as long as the acid is dilute.

Answer 3

False; it isn’t safe to react v. reactive metals (like calcium & lithium) with dilute acid.

Question 4

C1 Reactivity Trend

Which metals can you react with a dilute acid?

Answer 4

Small pieces of metals like magnesium, aluminium, zinc, iron & copper.

Question 5

C1 Reactivity Trend

What dilute acid should you use (to react with metals)?

Answer 5

Typically:
1) 1.0 mol/dm^3 HCl
2) or 0.5 mol/dm^3 H2SO4

Question 6

C1 Reactivity Trend

What is the general idea for the reactivity trend practical?

Answer 6

1) test each metal in acid at room T & record observations
2) for any metals that show no reaction or v. slow reaction, can warm mixture & record any further observations

Question 7

C1 Reactivity Trend

How do you warm something safely?

Answer 7

Ensure you wear eye protec..
Don’t overfill test tubes - should be no more than 1/4 full.
Can warm reaction mixture by placing test tube in beaker of hot water.
Have test tube rack ready to put test tube into post-warming.

Question 8

How do you warm something safely (specifically for using a Bunsen Burner)?

Answer 8

1) half-open air hole
2) hold test tube securely w/ test-tube holder
3) tilt test tube so it pts away from you & other people
4) hold test tube few cm above flame w/ liquid’s surface over flame
5) move test tube in & out of flame & take it away pre-boiling begins
6) have test tube rack ready to put test tube into post-warming

Question 9

C1 Reactivity Trend

How do you collect and test hydrogen?

Answer 9

Hydrogen is less dense than air so can collect it by upward delivery.
Hold empty test tube upside down over reaction mixture. Hydrogen will rise & fill test tube. Allow time to collect enough gas, then hold lighted splint to mouth of test tube & observe if there is a pop.

Question 10

How can you show reactivity trends?

Answer 10

Displacement reactions:
1) start by measuring out small amt halide salt solution in test tube
2) + few drops of halogen solution to it & shake tube gently
3) if colour change seen, then reaction has happened
-> halide has displaced halide ion from the salt
-> if no reaction occurs, won’t be colour change
4) repeat process w/ diff. combos of halide salt & hydrogen
5) table for diff. combos
6) chlorine displaces both bromine & iodine from salt solutions
7) bromine can’t displace chlorine, but does displace iodine
8) iodine can’t displace chlorine or bromine
9) -> shows reactivity trends
10) -> halogens get less reactive as you go down group (to do w/ how easily they gain e^-s)

Question 11

How do you show reactivity trends (table)?

Answer 11

start w/ / KCL(aq) - colourless / KBr(aq) - colourless / KI(aq) - colourless
add Cl2(aq) - colourless / no reaction / orange solution (Br2) formed / brown solution (I2) formed
add Br2(aq) - orange / no reaction / no reaction / brown solution (I2) formed
add I2(aq) - brown / no reaction / no reaction / no reaction

Question 12

How do you set up an electrochemical cell? (electrolysis of copper sulfate)

Answer 12

1) get 2 electrodes (should use inert electrodes - platinum or carbon); clean surfaces of electrodes w/ piece of emery paper (or sandpaper)
2) from -> pt on, be careful not to touch the surfaces of the metals w/ hands -> could transfer grease back onto strips
3) place both electrodes into beaker filled w/ ur electrolyte
4) connect electrodes to power supply using crocodile clips & wires

Question 13

How do you set up an experiment with non-inert electrodes?

Answer 13

1) non-inert electrodes can decompose into the electrolyte
2) e.g. could use copper electrodes in solution of copper sulfate
3) get 2 copper electrodes (not inert carbon or platinum 1s); clean surfaces of the electrodes w/ piece of emery paper (or sandpaper)
4) from -> pt on, be careful not to touch surfaces of metals w/ ur hands -> could transfer grease back onto strips
5) place both electrodes into beaker filled w/ ur electrolyte
6) connect electrodes to power supply using crocodile clips & wires
7) as reaction cont.s, mass of anode will decrease & mass of cathode will increase
-> bc copper is transferred from anode to cathode
8) reaction takes bit of time to happen, so will need to leave cell running for 30 mins or so to get decent change in mass
9) if want to measure how mass of electrodes has changes in experiment like this one, should dry electrodes before weighing them
-> any copper sulfate solution on electrodes may mean they appear to have higher mass than they rlly do

Question 14

What are the results for the electrolysis practical with inert electrodes and copper sulfate solution?

Answer 14

Solution of copper sulfate (CuSO4) contains 4 diff. ions: Cu^2+, SO4^2-, H^+ & OH^-.
1) copper metal is less reactive than hydrogen so at cathode, copper metal prod.d & you’d see coating of copper forming on cathode:
Cu^2+ + 2e^- -> Cu
2) aren’t any halide ions present so at anode, oxygen & water prod.d; ud see bubbles of gas forming:
4OH^- -> O2 + 2H2O + 4e^-

Question 15

What are the results for the electrolysis of copper sulfate solution using non-inert electrodes?

Answer 15

Non-inert electrodes can take part in electrolysis reactions.
Electrical supply acts by:
1) pulling electrons off copper atoms at anode, causing them to go into solution as Cu^2+ ions:
anode: Cu(s) -> Cu^2+(aq) + 2e^0
2) then offering electrons at cathode to nearby Cu^2+ ions to turn them back into copper atoms:
cathode: Cu^2+(aq) + 2e^- -> u(s)

Question 16

How do you conduct the thin-layer chromatography (TLC) practical?

Answer 16

1) draw line neat bottom of plate w/ pencil bc pencil marks are insoluble & won’t move w/ solvent as ink might
-> put spot of mixture to be separated on line
2) put ~ of solvent into beaker; dip bottom of plate (not spot) into solvent
3) put watch glass over beaker to stop any solvent from evaporating away
4) solvent will start to move up plate; when chemicals in mixture dissolve in solvent, they will move up plate too
5) will see diff. chem.s in sample separate out, forming spots at diff. places on plate
6) remove plate from beaker before solvent reaches top; mark distance solvent has moved (the solvent front) in pencil
-> can use -> technique to separate the diff. components of a dye

Question 17

Outline the set-up for the TLC practical.

Answer 17

1) watch glass
2) solvent front
3) plate
4) spot of unknown substance
5) point of origin
6) solvent

Question 18

How do you conduct the simple distillation practical?

Answer 18

Used for separating out liquid from solution:
1) pour sample of seawater into distillation flask
2) set up apparatus (diagram for this); connect bottom end of condenser to cold tap using rubber tubing; run cold water thru condenser to keep it cool
3) grad.ly heat distillation flask; part of solution w/ lowest bpt will evap, in this case, the water
4) water vapour passes into condenser where it cools & condenses (turns back into liquid), then flows into beaker where it’s collected
5) event.ly end up w/ salt left in flask

Question 19

Outline the set-up for the simple distillation practical.

Answer 19

1) thermometer
2) water out
3) condenser
4) water in
5) pure distilled water
6) seawater
7) heat

Question 20

How do you conduct the fractional distillation practical?

Answer 20

If mixtr of liquids, can separate it w/ fractional distillation; lab demo that can be used to model fractional distillation of crude oil at refinery:
1) put mixture in flask; attach fractionating column & condenser above flask (diagram for this)
2) grad.ly heat flask; diff. liquids will all have diff, bpts
-> so will evap at diff. Ts
3) liquid w/ lowest bpt evap.s 1st; when T on thermometer matches bpt of liquid, will reach top of column
4) liquids w/ higher bpts might also start to evap.
-> but column cooler towards top so will only get part of way up before condensing & running back down to flask
5) when 1st liquid has been collected, raise temperature until next 1 reaches top

Question 21

Outline the set-up for the fractional distillation practical.

Answer 21

1) thermometer
2) coldest bit of column
3) fractionating column filled w/ glass rods
4) hottest bit of column
5) crude oil substitute
6) heat
7) condenser
8) water out
9) water in
10) fractions collected at lower temperatures

Question 22

How do you test for anions? (halide ions)

Answer 22

To test for chloride ions (Cl^-), bromide ions (Br^-) or iodide ions (I^-):
1) add some dilute nitric acid (HNO3)
-> to 1st get rid of any carbonate ions which prod. pale ppt w/ silver nitrate too
-> can’t use HCl, bc that would add chloride ions
2) followed by few drops of silver nitrate solution (AgNO3)
a) chloride ions give white ppt of silver chloride:
Ag^+(aq) + Cl^-(aq) -> AgCl(s)
b) bromide ions give cream ppt of silver bromide:
Ag^+(aq) + Br^-(aq) -> AgBr(s)
c) iodide ions give yellow ppt of silver iodide:
Ag^+(aq) + I^-(aq) -> AgI(s)

Question 23

How do you test for anions? (carbonates)

Answer 23

1) to test for carbonate ions in solution, 1st add ~ barium chloride solution
-> if carbonate ions present, will prod. white ppt of barium carbonate
2) then + ~ dilute HCl
3) if carbonate ions present, mxtr will fizz
-> this bc carbonate will react w/ acid to prod. CO2 gas:
-> barium carbonate + acid -> barium ions + carbon dioxide + water
BaCO3(s) + 2H^+(aq) -> Ba^2+(aq) + CO2(g) + H2O(l)
4) if gas collected and passed thru limewater, limewater should turn cloudy
5) once all of barium carbonate has reacted, will end up w/ colourless solution containing Ba^2+ ions

Question 24

How do you test for anions? (sulfate ions)

Answer 24

1) test for sulfate ions in solution is similar to test for carbonate ions
2) add some barium chloride solution
-> if sulfate ions in solution, white ppt of barium sulfate will form:
barium ions + sulfate ions -> barium sulfate
Ba^2+(aq) + SO4^2-(aq) -> BaSO4(s)
3) then add some dilute hydrochloric acid to the test sample
4) barium sulfate will not react with dilute hydrochloric acid, so white ppt will not dissolve
-> that’s how u know you’ve got sulfate ions & not carbonate ions

Question 25

How would you conduct the test for cations? (metal ions)

Answer 25

Compounds of metals prod. charcteristic colour when heated in a flame. 1) can test for various metal ions by putting substance in flame & seeing what colour the flame goes a) lithium, Li^+, gives crimson red flame b) sodium, Na^+, gives yellow flame c) potassium, K^+, gves lilac flame d) calcium, Ca^2+, gives brick-red flame e) copper, Cu^2+, gives blue-green flame 2) to carry out flame test in lab, 1st clean nichrome wire loop by dipping it into hydrochloric acid & then rinsing it in deionised water 3) then dip wire into sample of metal compound & put loop in clear blue part of Bunsen flame (hottest bit) -> record what colour flame goes

Question 26

What must you note about the metal ions flame test?

Answer 26

1) metals always form +ve ions 2) test only works if mystery compound contains 1 type of metal ion -> otherwise confusing mxtr colours

Question 27

What colour do lithium ions give in the flame test?

Answer 27

Crimson red.

Question 28

What colour do sodium ions give in the flame test?

Answer 28

Yellow.

Question 29

What colour do potassium ions give in the flame test?

Answer 29

Lilac.

Question 30

What colour do calcium ions give in the flame test?

Answer 30

Brick-red.

Question 31

What colour do copper ions give in the flame test?

Answer 31

Blue-green.

Question 32

How do you conduct the metal ions test (sodium hydroxide)?

Answer 32

1) many metal hydroxides are insoluble and precipitate out of sodium when formed -> ~ of -> these have characteristic colour 2) for this test, add few drops of sodium hydroxide solution to solution of mystery compound 3) if hydroxide ppt forms, can use its colour to tell which metal ion was in compound a) calcium, Ca^2+ white b) copper, Cu^2+ blue c) iron(II), Fe^2+ green d) iron(III), Fe^3+ brown e) zinc, Zn^2+ white at 1st but redissolves in excess NaOH after to form colourless solution

Question 33

What colour does calcium, Ca^2+, go in the sodium hydroxide precipitate test?

Answer 33

White.

Question 34

What colour does copper, Cu^2+, go in the sodium hydroxide test?

Answer 34

Blue.

Question 35

What colour does iron(II), Fe^2+, go in the sodium hydroxide precipitate test?

Answer 35

Green.

Question 36

What colour does iron(III), Fe^3+, go in the sodium hydroxide precipitate test?

Answer 36

Brown.

Question 37

What colour does zinc, Zn^2+, go in the sodium hydroxide precipitate test?

Answer 37

White, at 1st, but then redissolves in excess NaOH to form colourless solution.

Question 38

What is the ionic equation for calcium, Ca^2+, in the sodium hydroxide test?

Answer 38

Ca^2+(aq) + 2OH^-(aq) -> Ca(OH)2(s)

Question 39

What is the ionic equation for copper, Cu^2+, in the sodium hydroxide test?

Answer 39

Cu^2+(aq) + 2OH^-(aq) -> Cu(OH)2(s)

Question 40

What is the ionic equation for iron(III), Fe^3+, in the sodium hydroxide test?

Answer 40

Fe^3+(aq) + 3OH^-(aq) -> Fe(OH)3(s)

Question 41

What is the ionic equation for iron (II), Fe^2+, in the sodium hydroxide precipitate test?

Answer 41

Fe^2+(aq) + 2OH^-(aq) -> Fe(OH)2(s)

Question 42

What is the ionic equation for zinc, Zn^2+, for the sodium hydroxide precipitate test?

Answer 42

Zn^2+(aq) + 2OH^-(aq) -> Zn(OH)2(s), then: Zn(OH)2(s) + 2OH^-(aq) -> Zn(OH)4^2-(aq)

Question 43

What are the ways of measuring the pH of a solution?

Answer 43

1) indicator & pH chart 2) pH probe & pH meter

Question 44

How can you measure the pH of a solution with a pH chart and indicator?

Answer 44

1) indicator: dye that changes colour depending on wherther it's above or below a certain pH 2) uni indicator: combo of dyes, v. useful for estimating pH of solution 3) indicators simple to use -> + few drops to solution testing, then compare colour solution goes to pH chart for that indicator

Question 45

How can you measure the pH of a solution using a pH probe?

Answer 45

1) pH probe is attached to a pH meter; can be used to measure pH electronically 2) probe placed in solution ur measuring & pH given on digital display as numerical value 3) -> gives higher level of accuracy than indicator 4) when using pH probe, important to calibrate it correcly (by setting it to read pH 7 in sample pf pure water) & rinse probe w/ deionised water in between readings

Question 46

How do you conduct the titration practical?

Answer 46

Allow u to find out exactly how much acid needed to neutralise given quant. of alkali (or vice versa). 1) fill burette w/ standard solution (known conc. of acid) -> keep burette below eye level while filling it -> don't wanna be looking up if any acid spills 2) use volumetric pipette to transfer 25.0cm^3 of sodium hydroxide solution to conical flask 3) add few drops of single indicator to flask -> can't use Uni bc changes colour grad.ly - want single colour change 4) gradually add acid from burette to flask, dropwise & swirling flask regularly, until indicator js changes colour 5) record start & end readings on burette so you can calculate the titre -> rough so don't need exact end-point, js note approximate amt acid needed then go slowly to this on next runs 6) repeat method until obtain concordant titres (similar readings, w/in 0.10cm^3 of each other)

Question 47

What is the end point?

Answer 47

When the indicator changes colour when all the alkali has been neutralised.

Question 48

How do the single change indicators change?

Answer 48

1) phenolphthalein: a) pink in alkalis b) colourless in acids 2) methyl orange a) yellow in alkalis b) red in acids

Question 49

What is the titre?

Answer 49

The volume of acid used to neutralise the alkali.

Question 50

How do you make potassium sulfate?

Answer 50

Can be made from potassium hydroxide & sulfuric acid: 1) put dilute potassium hydroxide solution, KOH (aq) into conical flask & add few drops of phenolphthalein indicator -> phenolphthalein changes colour at end-point of titration so adding indicator enables u to determine when alkali has been neutralised 2) add dilute sulfuric acid, H2SO4(aq) from burette or dropping pipette, stopping when indicator changes from pink to colourless 3) add 'activated charcoal' -> attracts the phenolphthalein & can filter mixture to remove the activated charcoal w/ phenolphthalein attached to it 4) warm filtrate to evap water, leaving potassium sulgfate behind -> must not be heated to dryness Hazard: potassium hydroxide is toxic

Question 51

How do you make ammonium sulfate?

Answer 51

Similar method to method for making potassium sulfate: 1) place dilute ammonia solution, NH3(aq), in conical flask w/ methyl oange indicator -> ammonia solution releases small amts ammonia in gas state which has irritating sharp smell, so must take care to avoid breathing it in 2) add dilute sulfuric acid, H2SO4(aq), from burette or dropping pippete, stopping when indicator changes from yellow to red 3) when end-point reached, can add lil extra ammonia solution to ensure reaction complete -> any remaning ammonia will be lost in evap.ion Hazards: ammonia solution alkaline & ammonia also gives off irritating sharp smell; excess ammonia given off in gas state when solution warmed

Question 52

How can you make soluble salts using acid / alkali reactions?

Answer 52

Using acid / alkali reactions: 1) soluble salts (salts that dissolve in water) can be made by reacting acid w/ alkali 2) -> but can't tell if reaction has finished -> no signal that all acid has been neutralised -> also can't js add excess of alkali to acid & filter out wht's left bc salt is soluble & would be contaminated w/ excess alkali 3) instead, have to add exactyly right amt alkali to neutralise acid -> can carry out titration to work out exact amt alkali needed 4) then, carry out reacion using exactly right proportions of alkali & acid -> but w/ no indicator (bc u know vols needed) so salt won't be contaminated w/ indicator 5) solution that remains when reaction complete contains only salt & water -> slowly evap off ~ of water & then leave solution to crystallise -> filter off solid & dry it -> be left w/ pure, dry salt

Question 53

How do you make an soluble salts using an acid and insoluble reactant?

Answer 53

1) can make soluble salts by reacting acid w/ insoluble base 2) need to pick right acid, plus metal or insoluble base (metal oxide or metal hydroxide) 3) add base to acid -> base & acid will react to prod. soluble salt (+ water) -> will know when acid has been neutralised bc excess solid will js sink to bottom of flask -> ~Ts need to heat reaction mxtr in this step to get acid & base to react 4) then filter off excess solid to get solution containing only salt & water 5) heat solution gently to slowly evap off ~ of water, then leave more conc.d solution to cool & allow salt to crystallise 6) filter off solid & leave to dry 7) EXAMPLE: can add copper oxide to hydrochloric acid to make copper chloride: CuO(s) + 2HCl(aq) -> CuCl2(aq) + H2O(l)

Question 54

What is the principle behind making insoluble salts with precipitation reactions?

Answer 54

1) to make pure, dry sample of insoluble salt, can use precipitation reation -> js need to pick right 2 soluble salts, they react & u get insoluble salt 2) EXAMPLE: to make lead chloride (insoluble salt), mix lead nitrate & sodium chloride (both soluble) lead nitrate + sodium chloride -> lead chloride + sodium nitrate Pb(NO3)2(aq) + 2NaCl(aq) -> PbCl2(s) + 2NaNO3(aq)

Question 55

What is the method for making insoluble salts with precipitation reactions?

Answer 55

1) add 1 spatula of lead nitrate to test tube a) add deionised water to dissolve the lead nitrate b) use deionised water to make sure there are no other ions abt c) shake it thoroughly to ensure all lead nitrate has dissolved d) then, in separate test tube, do same w/ spatula of sodium chloride 2) tip 2 solutions into small beaker & give good stir to ensure it's all mixed together; lead chloride should ppt out 3) put folded piece of filter paper into filter funnel & stick funnel into conical flask 4) pour contents of beaker into middle of filter paper; ensure solution doesn't go above filter paper -> otherwsie ~ of solid could dribble down side 5) swill out beaker w/ more deionised water & tip this into filter paper -> to ensure get all wanted prod. from beaker 6) rinse contents of filter paper w/ deionised water to ensure all soluble sodium nitrate has been washed away 7) then js scrape lead chloride onto fresh filter paper & leave to dry

Question 56

What are the investigations into rates of reaction to know?

Answer 56

1) reaction of HCl & marble chips 2) reaction of magnesium metal w/ dilute HCl

Question 57

What is the practical for the reaction of marble chips and hydrochloric acid? (rate experiments)

Answer 57

Can use this xp to show how SA affects reaction rate: 1) set apparatus up -> important system is air tight so no gas escapes 2) measure vol of gas prod.d w/ gas syringe -> take readings at regular time intervals & record results in table 3) can plot graph of results -> time on x-axis & volume on y-axis 4) repeat experiment w/ exactly same vol & conc. of acid and exactly same mass of marble chips, but w/ marble more crunched up 5) then repeat w/ same mass of powdered chalk -> marble & chalk both made of calcium carbonate (CaCO3)

Question 58

What is the reaction of magnesium metal with dilute hydrochloric acid?

Answer 58

1) reaction is good for measuring effects of changing conc. on reaction rate 2) reaction gives off hydrogen gas, so can measure loss of mass as gaas formed using mass balance 3) during xp, take readings of mass of flask & its contents at regular t intervals -> put results in table & work out loss in mass for each reading 4) can plot graph of results w/ time on x-axis & loss in mass on y-axis 5) repeat xp w/ exacly same mass & surface area of magnesium & exactly same vol of acid, but w/ diff. conc.s acid

Question 59

What are the results for the reaction of hydrochloric acid and marble chips?

Answer 59

1) using finer particles means marble has larger SA 2) the finer the particles are (& greater the SA of the solid reactants) the faster the reaction goes, as shown on graph 3) if greater mass of small chips added, extra SA gives faster reaction & also more gas evolved overall

Question 60

What are the results for the reaction of magnesium metal with dilute hydrochloric acid?

Answer 60

Higher conc. of acid gives faster reaction w/ reaction finishing sooner.

Question 61

What are the checks to be made? (electrolysis, electrical connections)

Answer 61

If you don't see changes in electrolysis cell, check: 1) ensure end of each electrode under surface of electrolyte 2) ensure electrical connections made securely, e.g. cleaning crocodile clips If still don't see any changes, replace each piece of apparatus in turn.

Question 62

How do you collect gases by displacement? (electrolysis)

Answer 62

1) fill each small test tube w/ electrolyte 2) quickly turn them upside down in beaker of electrolyte 3) aim is to keep open ends under surface 4) -> way, test tubes remain filled w/ electrolyte until you're ready to connect the battery

Question 63

How do you apply a sample to chromatography paper?

Answer 63

1) apply sample on baseline of chromatography paper 2) results will be more acc. if u conc. sample into small spot or line 3) if it's more spread out, diff. substances present in sample may tend to merge & streak 4) could use short length of capillary tube to apply sample a) dip 1 end of capillary tube in leaf extract b) put finger over other end, then briefly tap tube onto baseline c) allow spot to dry then add another spot on top 5) repeat process several times to obtain conc.d spot of leaf extract

Question 64

What should you know about using a thermometer?

Answer 64

1) ethanol-filled thermometers used in schools usually measure in range of -10C to 110C 2) mercury-filled thermometers measure in range -10C to 360C 3) to measure bpt of water, choose thermometer w/ max close to 100C 4) many thermometers have resolution of + or - 1C but some measure to + or - 0.5C or better 5) -> if u move thermometer, allow time for temp to settle before taking a reading

Question 65

What should you know about analysing compounds?

Answer 65

1) plan sequence of tests 2) if given unknown solutions to analyse, carry out ppt tests for cations & anions 1st bc they're easier to do than flame tests 3) if given unknown solids to analyse, could carry out flame tests & carbonate tests 1st, then make solutions for ppt tests 4) vital you work carefully & cleanly 5) will obtain false positive results is samples & test solutions become muddled or if u use same dropping pipette for each solution w/out thoroughly rinsing it w/ water each time 6) use small vols of unknown substances in test tubes for ppt tests 7) take care when performing practical bc some chem.s will be harmful or toxic, others may be corrosive 8) wear appropriate eye protecc.

Question 66

Which salts are soluble?

Answer 66

1) all sodium, potassium & ammonium salts 2) all nitrates 3) most chlorides, bromides & iodides -> excluding: chlorides, bromides & iodides of silver & lead 4) most sulfates -> excluding sulfates of lead, barium & calcium 5) sodium, potassium & ammonium carbonates

Question 67

Which salts are insoluble?

Answer 67

1) chlorides, bromides & iodides of silver & lead 2) sulfates of lead, barium & calcium 3) most carbonates -> excluding: sodium, potassium & ammonium carbonates

Question 68

Which solube salts do you make using the method of titrating acid with alkali?

Answer 68

1) potassium 2) sodium 3) calcium 4) magesium

Question 69

Which soluble salts do you make using the method of adding excess metal to acid, then filtering out the remaining metal?

Answer 69

1) magnesium 2) aluminium 3) zinc 4) iron

Question 70

Which soluble salts do you make using the method of adding excess insoluble base to acid, then filtering out the remaining base?

Answer 70

1) magnesium 2) aluminium 3) zinc 4) iron 5) copper 6) silver

Question 71

Which soluble salts do you make using the method of adding excess insoluble carbonate to acid, then filtering out remaining carbonate?

Answer 71

1) calcium 2) magnesium 3) aluminium - no carbonate (so no?) 4) zinc 5) iron - iron (II) only 6) copper 7) silver

Question 72

What is the general way of making an insoluble salt?

Answer 72

To make salt XY 1) mix X nitrate solution w/ sodium Y solutoin 2) -> e.g. to make insoluble lead iodide, would mix lead nitrate solution w/ sodium iodide solution 3) insoluble salt forms as ppt that you can separate from solution by filtering 4) can hen wash it w/ water & dry in warm overn 5) -> not salt you'll make in school lab

Question 73

What are the (general) ways of making a soluble salt containing metal ions?

Answer 73

1) titrate acid w/ alkali 2) add excess metal to acid, then filter out remaining metal 3) add excess insoluble base to acid, then filter out remaining base 4) add excess insoluble carbonate (most carbonates bar sodium, potassium & ammonium) to acid, then filter out remaining carbonate

Question 74

How do you make a soluble salt that doesn't contain metal ions?

Answer 74

To make ammonium salts by titrating a suitable acid w/ ammonia solution; then prod. dry salt by crystallisation: 1) HCl acid makes chlorides 2) sulfuric acid makes sulfates 3) nitric acid makes nitrates To make soluble salt containing metal ions, method you choose depends on metal involved.

Question 75

How do you set up an electrolysis cell?

Answer 75

1) need container for solution (electrolyte) & 2 electrodes connected to battery or power pack 2) electrode connected to negative terminal of battery of power pack becomes cathode 3) electrode connected to positive terminal becomes anode 4) can collect products in gas state in small test tubes so you can identify them later 5) remember electrolytes & their products may be harmful so wear eye protection

Question 76

How can you identify the products of electrolysis?

Answer 76

1) prod.s in solid state like copper usually appear as coating on electrode 2) can ID prod.s in g state using diff. tests: a) lighted splint ignites hydrogen w/ pop b) glowing splint relights in oxygen c) damp blue litmus paper turns red, then white, in chlorine -> take care: chlorine is toxic gas & eed to be esp. careful not to breathe it in if you're asthmatic

Question 77

How do you prepare leaf pigments for chromatography?

Answer 77

To extract pigments from plant cells, must break up leaves in presence of suitable solvent. 1) cut up some leaves finely 2) grind leaves for several mins in mortar w/ pinch of sand & lil propanone 3) could apply plant directly to strip of chromatography paper or may prefer to purify it 1st w/ filtration

Question 78

How do you carry out chromatography?

Answer 78

1) mark baseline on strip of chromatography paper, then apply small sample of leaf extract 2) place paper in stoppered boiling tube containing propanone as mobile phase 3) propanone level must be below baseline 4) remember to remove chromatography paper before solvent reaches top, mark level of solvent, then let it dry 5) for each coloured spot, record its shape, colour & Rf value

Question 79

How can you produce water by distillation?

Answer 79

1) must heat solution so water vapour (or steam, if boiling) evap.s from it 2) water vapour then colled & condensed 3) distillation apparatus including water-cooled condenser could be used & is effective, but can be complex to set up so simpler apparatus can be used instead 4) instead of condenser, delivery tube carries steam to boiling tube & boiling tube is in beaker of iced water to cool it 5) w/ -> sort of apparatus, take care to: a) avoid contact w/ steam bc can cause burns b) clamp apparatus securely so can't fall over 6) will need to adjust Bunsen burner flame to avoid excessive rate of boiling 7) may put insoluble anti-bumping granule or pieces of broken pot in conical flask 8) -> these help solution boil more evenly & safely, but still need to observe carefully & adjust flame

Question 80

How do you test the purity of your product? (distillation)

Answer 80

1) pure water boils at 100C at normal atmos pressure 2) can use thermometer or temperature probe connected to data logger to measure bpt of distillation prod. 3) water that contains dissolved substances has bpt higher than 100C