Practical Skills Flashcards
How do you measure the enthalpy of neutralisation?
- Use a polystyrene beaker, with a thermometer in solution.
- Add known volumes of acid and alkali together.
- Record the start and final temp to get temp rise.
- Stir solution to ensure mixture.
How do you measure enthalpy of dissolution?
- Use a polystyrene beaker, with a thermometer in solution.
- Add solid to water and dissolve.
- Record the start and final temp to get temp rise.
- Stir solution to ensure mixture.
How do you measure a displacement reaction?
- Use a polystyrene beaker, with a thermometer in solution.
- Add metal to salt solution.
- Record the start and final temp to get temp rise.
- Stir solution to ensure mixture.
How do you measure the enthalpy of combustion using a bomb calorimeter?
- Use a fuel to heat a volume of water above it.
- Weigh fuel before the experiment and after experiment.
- Burn the fuel and measure the temp change of the water.
- n=m/Mr
What are the problems when measuring enthalpy change?
Heat loss to surroundings.
Heat loss to container.
Incomplete combustion.
Flammable liquids used which evaporate.
What are the control variables of the investigation of how rate of reaction changes with temperature?
Volume and conc. of solutions.
Mass and surface area of any solids.
What calculation is used to work out rate of reaction?
Amount of reactant used or product formed/time
How do you measure the formation of a precipitate in an investigation of how rate of reaction changes with temperature?
- Put conical flask contain solution on white paper w/ cross.
- Time how long for the cross to no longer be visible.
- We do this at different temperatures.
How do we measure gases produced in an investigation of how rate of reaction changes with temperature?
- Gas produced when mixing reactant together.
- Mass in change measure at regular time intervals on a mass balance.
How do you measure the gas change using a had change in an investigation of how rate of reaction changes with temperature?
- Measure volume of gas produced at regular time intervals after mixing the reactants together.
How do you distill a product from a reaction?
- Gently heat to boil the mixture.
- Chemicals evaporate.
- Cool water in condenser cools gas, so they condense.
- Liquid collected.
What equipment is used in the distillation of a product from a reaction?
- Round-bottom flask attached to a thermometer.
- Condenser is horizontal.
How do you separate the distillation of a product from a reaction?
- Transfer first distillation to separating funnel.
- Leave to settle into layers.
- Drain off and separate layers
How do you test for an alcohol?
- Add acidified potassium dichromate (Orange) and gently warm.
- A positive reaction goes green.
- If the reaction from a primary alcohol is distilled an aldehyde is made, if the reaction is refluxed a carboxylic acid is made.
- If the reaction from a secondary alcohol is refluxed a ketone is made.
- No reaction will occur with a tertiary alcohol.
How do you test for aldehydes and ketones?
Tollens reagent
Silver mirror forms is aldehyde is present.
