CHEMISTRY, Moles, Chemical Calculations and yields Flashcards
Why are moles useful?
Atoms are too small to weigh individually so it’s easier to weigh a mole of something
What is a mole?
a unit to measure the amount of a chemical we have
What is the equation for the number of moles in a sample?
mass of the substance/Mr
What is theoretical yield?
The expected amount of a product if all of our reactant is used
What is the equation for percentage yield?
Actual yield produced/Theoretical yield of product x100
Equation for percentage of atom economy?
Mr of the desired products / Mr of all reactants x100
What is titration?
A technique that can be used to find out the concentration of an acid or an alkali.
How can uncertainty be measured and how do you work it out?
By considering the resolution of the scientific equipment being used and from the range of the set of data. It’s the range/2
What is Avogrado’s number?
6.02 x10 to the power of 23, number of particles in a mole.
What happens when doing chemical calculations if the range gets larger?
More chance of error
What are the tools needed in a titration practical?
pipette, burette, safety pipette filler, conical flask
What is thermal decomposition?
A chemical reaction that happens when a compound is broken down when heated.
What is the law of conservation of mass?
Matter can not be created or destroyed no matter how they are arranged.
What is the equation for the concentration of a solution?
The amount of a substance/ The volume of the solvent
What is the equation for working out moles of a gas?
Volume/molar gas volume (Vm)
Why can we never have 100% yield in a reaction?
Other unexpected reactions can occur that don’t produce the desired product and sometimes not all of the reactants are used in the reaction.
What is atom economy?
A measure of how many of the reactant atoms form a desired product.
What are the preparation steps before doing a titration practical?
- pipette should be rinsed with deionised water.
2.Safety pipette filler is used to draw up the solution until bottom of menicis is on line then poured into conical flask.
3.Burette is rinsed and then filled with solution ensuring the jet is filled.
What is the method for the titration practical.
- Use the pipette and pipette filler to add the sodium hydroxide to conical flask.
- Add a few drops of indicator and put conical flask on white tile.
- Fill burette with hydrochloric acid and note reading.
- Add acid from burette to the conical flask and mix it.
- Stop adding acid when the indicator changes colour and then repeat the steps until the concordant titres.
