Required Practicals Flashcards
What is the aim of *RP1 - making a salt?
To prepare a pure, dry sample of a salt from an insoluble metal oxide base (copper (II) oxide) and an acid (sulfuric acid). (C5.5 & 5.6)
Base + Acid —> Water + Salt
What is the word, symbol and ionic equation for the reaction for RP1? What is the equipment needed for RP1?
Word: Copper (II) Oxide + Sulfuric Acid —> Copper Sulfate + Water
Symbol: CuO(s) + H2SO4(aq) —> *CuSO4 (aq) + H2O(l) *CuSO4 = Cu[2+] & SO4[2-]
Ionic: CuO(s) + H[+] —> Cu[2+] + H2O(l)
Equipment:
- Copper (II) oxide powder
- 20cm^3 of 1mol/dm^3 of sulfuric acid
- Measuring cylinder
- 2x Beakers
- Glass rod
- Bunsen burner
- Filter funnel and paper
- Evaporating basin
- Conical flask
- Tongs
What is the health and safety for RP1?
- Wear safety glasses.
- Warm acid gently.
- Be aware of chemicals.
What is the method for RP1?
1) After gently warming (to increase the speed/rate of reaction) the acid (DO NOT BOIL), add insoluble copper (II) oxide to sulfuric acid and stir.
2) The solution turns blue as the reaction occurs, showing that the copper sulphate is being formed. Keep adding copper (II) oxide powder until no more dissloves. Excess black copper oxide will form.
3) Filter the solution to remove excess copper oxide.
4) Pour filtered solution into the evaporating basin and gently heat over a water bath. Keep heating until crystals start to form.
5) Remove evaporating basin from the heat and leave to crystallise.
After some time, you should have some blue rhombic-shaped copper sulfate crystals.
What is the conclusion and the observations for RP1?
Conclusion: Base + Acid —> Salt + Water
Observations:
- When the copper oxide was added, the acid and base reacted, forming a blue solution.
- When excess copper oxide was added, there were black particles in the solution floating. This indicated that all the acid we’d started with had been NEUTRALISED.
How do you work out the formulae of acids? What are the charges on some common ions?
You need to know the common ions:
Sodium = Na+ Lithium = Li+ Potassium = K+ Ammonium = NH4+
Magnesium = Mg2+ Calcium = Ca2+ Copper = Cu2+ Zinc = Zn2+
Aluminium = Al3+
Chlorine = Cl- Bromine = Br - Iodine = I- Nitrate = NO3-
Oxygen = O 2- Sulfate = SO4 2- Carbonate = CO3 2-
What is the aim of *RP2 - Titration?
To use a titration to accurately measure the volume of acid (HCl), needed to neutralise a measured volume of alkali (NaOH).
What is the equipment needed for RP2?
- Volumetric Pipette - transfers fixed volume of alkali into conical flask
- Pipette Filler
- Conical Flask
- Burette - measures volume of acid added
- Acid-based indicator
- Distilled water
- Clamp and Stand
- Hydrochloric Acid (HCl)
- Sodium Hydroxide (NaOH) - 25cm^3
- Safety Goggles
- White tile - see the colour change
What is the health and safety for RP2?
- Eye protection
- HCl and NaOH are both irritants.
What is the method for RP2?
1) In a clean, dry pipette, transfer 25cm^3 of alkali into a conical flask.
2) Add a few drops of a suitable acid-based indicator to the alkali.
3) Fill a clean, dry burette with acid.
4) Note the starting volume.
5) Slowly add acid into the conical flask and gently swirl the conical flask.
6) When the indicator starts to change colour, add the acid ONE DROP at a time and continue to swirl.
7) Once the colour change lasts 10 seconds, stop adding acid, note the new volume.
8) Calculate the titration and *repeat until two concordant results are obtained. (Within 0.1cm^3).
* You can clean the flask with distilled water in between titrations. You don’t need to let it dry as water doesn’t affect the number of moles of NaOH present.
What calculations must you do to work out the concentration of the NaOH used to neutralise the acid?
1) Moles of HCl:
Moles = C (mol/dm^3) x V (cm^3) / 1000
2) Moles of NaOH —> Balanced equation (molar ratio)
3) Concentration of NaOH (mol/dm^3) = n. of moles / volume (cm^3) x 1000
Optional:
4) Concentration in g/dm^3
= Mr of NaOH x Conc (mol/dm^3)
What is the conclusion for RP2?
The volume of HCl needed to neutralise 25cm^3 of NaOH is between 24.3cm^3 and 24.4cm^3.
I also know that the concentration of the NaOH in g/dm^3 = 3.9g/dm^3.
What is the aim of RP3 - Electrolysis?
To accurately predict and observe the products formed at the electrodes during the electrolysis of 4 AQUEOUS ionic compounds.
What is the equipment needed for RP3?
- 1 beaker with *graphite electrodes (graphite can conduct electricity and heat excellently)
- retort stand and clamp to hold electrodes
- DC power supply (6 V)
- 2 x leads
- 2 x crocodile clips
- 1 mol/dm3 copper(II) chloride
- 1 mol/dm3 copper (II) sulfate
- 1 mol/dm3 sodium sulfate
- 1 mol/dm^3 sodium chloride
- blue litmus paper
What is the health and safety for RP3?
- Don’t leave cell running for more than 5 minutes.
- Ventilate room (Chlorine gas is toxic)
- Copper compounds are harmful
- Use a low voltage (no higher than 6V)
What is the method for RP3?
1) Set up the electrolysis circuit and clean the electrodes lightly using emery paper.
2) Half fill a 100 cm3 beaker with one of the solutions.
3) Connect the circuit and check that the light bulb is on to ensure that the circuit is working correctly.
4) Observe and record bubbling or metal coating at both electrodes. If there is bubbling, test the gas. If not, turn off the cell and observe the metal coating
5) If you’ve identified the gases and/or metal coating at both electrodes, turn off the cell and repeat with the next solution.
