required practicals Flashcards
1
Q
Describe a method for making pure crystals of magnesium chloride from magnesium and dilute hydrochloric acid
A
- put hydrochloric acid in a beaker
- add small pieces of magnesium ribbon
- until magnesium is in excess / until no more effervescence occurs
- filter using filter paper and funnel
- filter excess magnesium
- pour solution into evaporating basin / dish
- heat using Bunsen burner
- leave to crystallize
- decant (gradually pour to remove solids) solution
- pat dry using filter paper
2
Q
The student carried out a titration to find out the volume of 0.100 mol / dm3 sulfuric acid needed to neutralize the sodium hydroxide. Describe how the student would complete the titration.
A
- use a pipette to add sodium hydroxide of unknown concentration to a conical flask
- add an indicator like phenolphthalein, methyl orange
- add the sulfuric acid from a burette
- until the indicator just changes color / dropwise towards the end
point while swirling - until the indicator changes from pink to colorless (for phenolphthalein) / yellow to red (for methyl orange)
3
Q
Describe how to investigate what happens when copper chloride solution (aqueous solutions) undergoes electrolysis
A
- Pour 50cm^3 of copper chloride into a beaker
- Place a plastic petri dish that has 2 holes over the beaker
- Insert a carbon graphite(inert) rod into each hole as electrodes
making sure they don’t touch each other - Attach crocodile leads to the rods and connect these to the
terminals of a low voltage power supply - Switch on the power supply and observe reactions at both electrodes
- At the negative electrode(cathode), its coated with copper. At
positive electrode there are bubbles, place litmus paper near and its
bleached white so chorine is produced.
4
Q
Investigate the temperature change during the reaction between citric acid and sodium hydrogen carbonate solution.
A
- Pour 25cm^3 of sodium hydrogen carbonate solution into a polystyrene cup
- Measure the temperature of this solution
- Add 0.2g of citric acid to the cup
- Stir the solution
- Measure the temperature of the solution
- Repeat steps 3 to 5 until 2g of citric acid has been added
