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Chemistry > Paper 2 Practicals > Flashcards

Paper 2 Practicals Flashcards

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1
Q

What is the formula for rate of reaction?

A 
                 time
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2
Q

What are the 3 ways of measuring rate of reaction?

A
  • Precipitation and Colour change
  • Change in Mass (usually gas given off)
  • Volume of Gas given off
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3
Q

Rate of reaction: How do you measure precipitation and colour change?

A
  • visual changes (solution goes from transparent to opaque)
    Observe a mark through the solution, measure how long it takes to disappear.
  • colour to colourless-> how long it takes for the change to occur

SUBJECTIVE method, people may disagree
CANNOT plot rate of reaction graph

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4
Q

Rate of reaction: How do you measure change in mass?

A
  • Measure the speed of reaction that produces a gas (using mass balance)
  • gas released, mass disappearing is shown on balance
  • quicker reading drops, faster the reaction

CAN plot a rate of reaction graph if measurements taken at intervals
MOST ACCURATE method, mass balance is accurate
DISADVANTAGE-> released gas straight into room

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5
Q

Rate of reaction: How do you measure volume of gas given off?

A
  • Gas syringe/measuring cylinder in tub of water
  • more gas given off, faster reaction

GAS SYRINGE HAVE ACCURATE VOLUMES
CAN plot rate of reaction graph

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6
Q

How does concentration effect the rate of reaction?
(sodium thiosulfate + hcl)

A
  • Add 10cm3 of sodium thiosulfate to a conical flask using a measuring cylinder
  • place the flask on a printed black flask
  • add 10cm3 of HCL to the solution
  • swirl the solution and start a timer
  • look down through the top of the flask, after a certain time, solution will turn cloudy
  • stop the clock when the cross is no longer visible
  • repeat the experiment with lower concentrations of sodium thiosulfate solution
  • repeat the whole experiment to get mean values for each concentration
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7
Q

How does concentration effect the rate of reaction: Why does a solution go cloudy?

A

sodium thiosulfate + hcl-> sulfur (s) + etc
- sulfur is a solid, makes solution go cloudy

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8
Q

How does concentration effect the rate of reaction?
(sodium thiosulfate + hcl) : What is the issue with reproducibility?

A
  • The disappearing cross is subjective, different people could say different things, therefore making the results hard to exactly reproduce
  • people have different eye sights
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9
Q

How does concentration effect the rate of reaction?
(magnesium + HCL)

A
  • place 50cm3 of HCL in a conical flask using a measuring cylinder
  • attach the conical flask to a bung and delivery tube
  • place delivery tube in a container full of water, placing an upturned measuring cylinder also filled with water over the delivery tube
  • add a 3cm strip of magnesium to the acid and start a stop watch
  • reaction produces hydrogen gas, trapped in the measuring cylinder
  • measure volume of gas in cylinder every 10 seconds, continue until no more gas is produced
  • repeat the experiment to then calculate a mean, then repeating the experiment for different concentrations of HCL
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10
Q

Rate of reaction: What effect does concentration have on rate of reaction?

A

the higher the concentration, the faster the rate of reaction

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11
Q

Flame tests: What colour flame does Lithium (Li+) produce?

A

Red/Crimson

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12
Q

Flame tests: What colour flame does Calcium (Ca2+) produce?

A

Red-orange

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12
Q

Flame tests: What colour flame does Pottasium (K+) produce?

A

Lilac

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12
Q

Flame tests: What colour flame does Sodium (Na+) produce?

A

Yellow

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13
Q

Flame tests: What colour flame does Copper (Cu2+) produce?

A

Green-blue

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13
Q

How do you test to identify a metal ion by using a flame test?

A
  • Take a nichrome wire, dip it in HCL and put it in a blue bunsen flame to clean it
  • Dip the nichrome wire in HCL again and then into the solid sample
  • Put the sample on he wire into the blue flame and observe the colour.
14
Q

How do you test to identify a metal ion by using sodium hydroxide solution?
(precipitation test)

A
  • Add a few drops of NaOH to 1cm3 of a metal ion solution in a test tube and record any observations
  • then add a further 1cm2 of NaOH to each solution to see if that creates any further change
15
Q

Precipitation test: what change is observed when NaOH is added to Calcium (Ca2+) ?

A

Cloudy with Precipitate

16
Q

Precipitation test: what change is observed when NaOH is added to Copper(II) (Cu2+)?

A

Blue with precipitate

16
Q

Precipitation test: what change is observed when NaOH is added to Magnesium (Mg2+)?

A

Cloudy

17
Q

Precipitation test: what change is observed when NaOH is added to Aluminium (Al3+) ?

A

white precipitate

17
Q

Precipitation test: what change is observed when NaOH is added to Iron (II) (Fe2+)?

A

Green with precipitate

18
Q

Precipitation test: what change is observed when NaOH is added to Iron (III) (Fe3+) ?

A

Yellow with orange precipitate

19
Q

What is paper chromatography?

A

it is a technique to seperate different dyes in an ink

20
Q

How do you do Paper Chromatography?

A

1-Draw a line in pencil near the bottom of a sheet of filter paper (pen is soluble, will disrupt the experiment, ink)
2- Add a spot of ink to the line, place the paper in a beaker of solvent (water, depends on what is being tested so can be ethanol)
3- Make sure ink isn’t touching the solvent
4- place a lid on the beaker to stop the solvent evaporating
5- the solvent slowly seeps up the paper, carrying the ink
6- each dye will move up the paper at a different rate, so they will seperate out, forming a spot in seperate places
7- If any dye is insolvent it will stay on the baseline
8- when the solvent has nearly reached the top of the paper, take it out and leave the paper to dry, leaving a pattern of spots (chromatogram)

21
Q

How do you analyse a sample of water for its purity?

A
  • Check pH of water by placing a sample of the water onto a universal indicator piece of paper
  • if it is pH 7= green, if it isn’t 7= acid or alkali dissolved in substance
    1- Use a balance to weigh an empty evaporating basin + record mass
    2- Fill evaporating basin with water sample, then place it on a tripod and gauze
    3- Use a bunsen burner to gently heat the water until it is all evaporated
    4- Allow evaporating basin to cool before reweighing-> if the sample contained any dissolved solids, the mass of the basin would have increased (crystals left in the basin
    5- IF the mass didn’t increase, shows the sample didn’t contain dissolved solids, so could be pure (could contain dissolved gases)
22
Q

How can water be purified by distillation?

A

1- Place a conical flask on top of a tripod and gauze, containing the water sample. The top of a conical flask has a delivery tube pointing to a test tube, which sits in a beaker containing ice and water
2- Gently heat the water using a bunsen burner until its boiling gently, evaporating into water vapour
3- Water vapour then travels along the connecting tube, condensing when it enters the cold test tube into liquid (distilled water)
4- Distilled water= no dissolved solids + pH 7 so pure water

Chemistry (13 decks)

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