Paper 1 Practicals Flashcards
What is a salt?
- contain a positive ion
- contains a negative ion
How do you make crystals from a soluble salt?
- Place a bunsen burner on top of a heatproof mat. Place a tripod with gauze and a breaker on top.
- Gently heat a fixed volume of Sulfuric acid within the beaker until almost boiling
- Use a spatula to add small amount of Copper Oxide to the solution, then stir in with a glass rod. The CuO should seem to disappear and the solution will turn a blue colour
- Keep adding CuO until some powder remains in the blue solution (shows the reactant has stopped, acid has stopped reacting)
- Use a funnel with filter paper and a conical flask to filter the insoluble CuO, leaving the filtrate (CuSO4)
- Place the copper sulfate solution in an evaporating basin and heat it gently over a beaker of boiling water.
- Leave the solution in a cool place for the Copper Sulfate crystals to form
What is a limiting reactant?
The reactant in a reaction that runs out first
What is a titration?
The solution of a known concentration is used to find the concentration of an unknown solution
What is the method of Titration?
- Use a pipette to transfer 25cm3 of an alkali into a conical flask
- Add 5 drops of an indicator (methyl orange etc) to the alkali
- Place conical flask on a white tile (see changed more clearly)
- Fill a biuret with acid
- Add just enough acid to the alkali until it is neutral
- Once a colour change occurs, add acid in drop by drop until the solution is neutral
- swirl the mixture to make sure the acid and alkali mix
- read volume of acid added from the biuret
- repeat the experiment until you get and overall 3 concordant results, take a mean for final volume (increases accuracy)
Titration: What will the colour change be for Methyl Orange?
Orange-> Red
Titration: How do you read from a biuret?
- eye is level with the surface of the liquid
- read from the bottom of the meniscus
What does concordant results mean?
Within 0.2 cm3 of each other
How do you investigate the effect on Aqueous solutions when undergoing electrolysis?
(Copper II Chloride)
1- pour 50cm3 of Copper II Chloride solution into a beaker
2- place a plastic petri dish over the beaker, with 2 holes
3- insert carbon graphite rods into each of the holes (electrodes)
4- connect wires to the rods with crocodile clips, connecting them to a low-voltage battery pack (4V, switch on)
5- cathode (-ve) is coated with copper, less reactive than hydrogen-> discharged at the cathode
6- anode: bubbles of gas, smell of chlorine-> halogen = discharged at anode
7-
What does inert mean?
unreactive
Why must the electrodes not touch?
It would produce a short circuit
Copper II Chloride: If you hold a piece of damp blue litmus paper near the anode what happens?
The anode is producing chlorine gas so bleaches the paper. (proves gas is chlorine)
How do you investigate the effect on Aqueous solutions when undergoing electrolysis?
(Sodium Chloride solution)
1- pour 50cm3 of Sodium Chloride solution into a beaker
2- place a plastic petri dish over the beaker, with 2 holes
3- insert carbon graphite rods into each of the holes (electrodes)
4- connect wires to the rods with crocodile clips, connecting them to a low-voltage battery pack (4V, switch on)
5- anode (+ve): bubbles of gas, bleaches litmus paper= chlorine (Halide, halogen discharged at the anode)
6- cathode (-ve): bubbles of gas, hydrogen. Sodium is MORE reactive, hydrogen is discharged at cathode. Use lit splint, squeaky pop test
How do you investigate the temperature change of an exothermic reaction?
(Neutralisation reaction-> NaOH + HCL)
1- use a measuring cylinder 30cm^3 of dilute HCL
2- transfer the acid into a polystyrene cup
3- Stand the polystyrene cup inside the beaker, stopping the cup from falling over
4- Use thermometer to measure temp of the acid, record data
5- use a measuring cylinder to measure 5cm^3 of Sodium Hydroxide solution, transfer to polystyrene cup
6- Fit plastic lid to cup with hole, place thermometer through hole (bulb must be submerged in the solution), gently stirring the solution.
7- exothermic reaction, temperature will increase, record highest temp reached
8- Rinse cup and repeat experiment
9- repeat again twice with 10cm^3 of Sodium Hydroxide solution
10- repeat several more times, each time increases amount of Sodium Hydroxide by 5cm^3 until max of 40cm^3, 2 results for each volume of NaOH
11- calculate mean value for max temp reached for each volume, then plot graph of results
What is the Independent, Control and Dependant variables of a Neutralisation reaction of NaOH and HCL?
Independent: Volume of Sodium Hydroxide solution
Dependant: Maximum temperature reached
Control: Volume of HCL, Concentration of both solutions
What is the relationship between temperature reached and volume of NaOH?
As volume increases, temperature increases as if there are more Sodium Hydroxide particles, there will be more reactions with the HCL particles
HOWEVER, at a certain point of adding NaOH, the max temp starts to decrease, as there is TOO much NaOH and not is HCl to react (some NaOH is unable to react.)
Why does maximum temperature begin to decrease at a certain volume of NaOH?
Energy released is spread over a larger volume, so when there is large volumes of NaOH, max temp decreases
Temp change: Why do you use a polystyrene cup with a lid?
Polystyrene is a good thermal insulator, reduced heat loss
Lid reduced heat loss to the air
How do you explain the method of filtration?
- Cut a piece of filter paper into a circle, then cut a small triangle into the paper so you can fold it into a cone
- Use a folded filter paper cone and place it in the funnel
- pour solution containing insoluble solid into the filter paper, separating the liquid reaction mixture from the solid.
How do you explain the Method of Evapouration?
- Pour solution into evaporating dish
- slowly heat the solution-> the solvent will evaporate and solution becomes more concentration, eventually crystals form
- keep heating until liquids have evaporated and only dry crystals are left
How do you explain the Method of Crystallisation?
-Pour solution into an evaporating dish and gently heat solution -> solvent will evaporate and solution becomes more concentrated
- When crystals begin to form, remove the dish from the heat and leave the solution to cool
- Salt begins to form crystals, insoluble in the cold
- Filter crystals out of solution, leave in warm place to dry (eg drying oven, in the sun)
What is Rock salt?
A mixture of salt and sand
- used on the roads in the winter
How can you seperate Rock salt?
Using Filtration and Crystallisation
- Grind the mixture (salt crystals are small), so it dissolves easy
- Put mixture in water and stir (salt dissolves, sand doesn’t)
- Filter mixture, collect sand on paper and solution (containing salt) in beaker
- Evaporate water from salt, creates dry crystals
What is distillation?
A separating process used to seperate mixtures containing liquids
How do you explain the process of Simple Distillation?
- Heat the solution, part of the solution with the lowest Boiling point evapourates first
- Vapour rises and then is cooled and condensed in the condenser, where it turns back into a liquid and is recollected
- Rest of the solution is left behind in the flask
- Saltwater-> seperate water and salt
- Can only use for substances with very different boiling points, otherwise will mix again as vapour.
How do you explain the process of Fractional Distillation?
Used to seperate a mixture of multiple liquids
- Place mixture in a flask with a fractioning column on top, then heat it up
- different liquids have different boiling points so evaporate at different temperatures (Lowest BP evaporates first)
- When the temp on the thermometer matches its BP, it reaches the top of the column, it is condensed in the condenser and collected
- Liquids with higher BP may also being to evaporate, but will condense before reaching the top as it gets colder further up the fractioning column
- When the first liquid is fully collected, raise the temperature until the next one reaches the top.
