Random Practicals Flashcards
Using combustion to form Empirical formulae
Use crucible and heat till red hot to sterelise and remove any traces of other substances.
Leave to cool then weigh with its lid
Add some clean magnesium ribbon and reweight with lid on.
Heat crucible - lid on to prevent bits escaping but keep lid on to allow oxygen in.
Heat strongly until all the magnesium ribbon has turned white (magnesium oxide)
Allow to cool then reweigh with lid and contents.
This mass - initial mass = mass of magnesium oxide.
How do you find the empirical formula through reduction?
Place a rubber bung into the test tube with a hole in the end - weigh
Place copper oxide in the test tube and - weigh
Turn on the gas to expel the air from the test tube. After 5 seconds light the gas coming out the hole.
Using the bunsen burner, heat the copper oxide for 10 minutes until the copper oxide turns from black to brownish pink
Turn off the bunsen burner and leave to cool
Turn off the gas and weigh the test tube, bung and its contents
Prepare soluble salt using an acid and an insoluble base
Use copper oxide and sulfuric acid to make copper sulfate.
Heat the acid in a water bath to speed up the rate of reaction
Then add the base- copper oxide - in excess to ensure all of the acid reacts
Keep adding until the copper sulfate is no longer clear blue stop adding the copper oxide when it does not react (stays black). Mix.
Filter off excess base so you are left with only soluble salt + water
Heat the solution in an evaporating basin gently using a bunsen burner and hot water bath until half the solution remains. Dipping glass rod in and seeing if crystals form.
Leave solution for 24 hours to allow crystal formation. Filter off solid salt and leave to dry.
Crystals are copper sulfate
Calorimetry experiments to find out enthalpy change for displacement and dissolving
Ensure reactants are all at the same temperature and mix in a polystyrene cup. Then measure the temperature change.
Biggest issue is energy loss so place polystyrene cup in a beaker of cotton wool to insulate.
Lid on top reduces energy lost through evaporation
Calorimetry experiments to find out enthalpy change for neutralisation
Place 25cm^3 of an acid (HCl) and 25cm^3 of a base (sodium hydroxide) in separate test tubes.
Heat in a water bath to 25C
Add both to a polystyrene cup and mix.
Record the temperature every 30 seconds and record the highest temperature.
Calorimetry experiments to find out enthalpy change for combustion
50g of water in a copper can - Good Conductor of heat - and record temperature.
Surround by draught excluder to reduce energy lost
Weight spirit burner and lid
Place the spirit burner underneath the can and light the wick
Stir the water constantly until the water reaches 50C and then cap the burner.
Weigh the spirit burner and lid again.
Calculate energy transferred using Q=MC∆T
Then to find energy produced by 1g of substance Q/Change in mass of burner
Rate of Reaction formula?
Amount of reactant used or amount of product formed / time
Investigate the effect of changing the surface of marble chips on the rate of reaction?
Add dilute HCl to marble chips into a conical flask - with gas syringe on top
Measure the volume of gas produced in a set time - taking readings at regular intervals
Repeat the experiment with different surface areas but the same mass and concentration of acid
Investigate the effect of different solids on the catalytic decomposition of hydrogen peroxide solution?
Hydrogen peroxide breaks down into water and oxygen
Place hydrogen peroxide in a conical flask with different solid (catalysts) with a gas syringe on top.
Measure the volume at regular intervals
Repeat with different catalysts
Ammonium Chloride reversible reaction?
When heated turns into ammonium gas and hydrogen chloride gas in the forward reaction.
When cooled turns back into ammonium chloride
Reaction of alklanes and halogens?
Alkane and halogen react in the presence of UV light to form Haloalkane.
1 hydrogen is replaced by a halogen
What is the state and colour of chlorine at room temperature?
Green gas
Colour and state of bromine at room temperature
Red brown liquid which gives off an orange vapour
Colour and state of Iodine?
Dark grey crystalline solid which gives off purple vapour when heated
Metal + water ?
Metal Hydroxide + Hydrogen
