Paper 2 Practicals Flashcards
What is the formula for rate of reaction?
time
What are the 3 ways of measuring rate of reaction?
- Precipitation and Colour change
- Change in Mass (usually gas given off)
- Volume of Gas given off
Rate of reaction: How do you measure precipitation and colour change?
- 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
Rate of reaction: How do you measure change in mass?
- 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
Rate of reaction: How do you measure volume of gas given off?
- 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
How does concentration effect the rate of reaction?
(sodium thiosulfate + hcl)
- 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
How does concentration effect the rate of reaction: Why does a solution go cloudy?
sodium thiosulfate + hcl-> sulfur (s) + etc
- sulfur is a solid, makes solution go cloudy
How does concentration effect the rate of reaction?
(sodium thiosulfate + hcl) : What is the issue with reproducibility?
- The disappearing cross is subjective, different people could say different things, therefore making the results hard to exactly reproduce
- people have different eye sights
How does concentration effect the rate of reaction?
(magnesium + HCL)
- 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
Rate of reaction: What effect does concentration have on rate of reaction?
the higher the concentration, the faster the rate of reaction
Flame tests: What colour flame does Lithium (Li+) produce?
Red/Crimson
Flame tests: What colour flame does Calcium (Ca2+) produce?
Red-orange
Flame tests: What colour flame does Pottasium (K+) produce?
Lilac
Flame tests: What colour flame does Sodium (Na+) produce?
Yellow
Flame tests: What colour flame does Copper (Cu2+) produce?
Green-blue
How do you test to identify a metal ion by using a flame test?
- 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.
How do you test to identify a metal ion by using sodium hydroxide solution?
(precipitation test)
- 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
Precipitation test: what change is observed when NaOH is added to Calcium (Ca2+) ?
Cloudy with Precipitate
Precipitation test: what change is observed when NaOH is added to Copper(II) (Cu2+)?
Blue with precipitate
Precipitation test: what change is observed when NaOH is added to Magnesium (Mg2+)?
Cloudy
Precipitation test: what change is observed when NaOH is added to Aluminium (Al3+) ?
white precipitate
Precipitation test: what change is observed when NaOH is added to Iron (II) (Fe2+)?
Green with precipitate
Precipitation test: what change is observed when NaOH is added to Iron (III) (Fe3+) ?
Yellow with orange precipitate
What is paper chromatography?
it is a technique to seperate different dyes in an ink
How do you do Paper Chromatography?
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)
How do you analyse a sample of water for its purity?
- 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)
How can water be purified by distillation?
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
