amount of a substance Flashcards
There is a number that is important to chemists, what is the name?
Avogadro’s Number
What is the value of avogadro’s number
6.02 x 10 to the power of 23
What does the mole contain?
6.02 x 10 to the power of 23
Ways of calculating moles
mass: moles/ molar mass
solution: concentration x volume
gas@RTP: volume/24000
gas not @RTP: (pressure x volume)/ (gas constant x temperature)
What is molar mass (relative formula mass)?
The molar mass or relative formula mass of a compound is the mass of one mole of that substance
What is the empirical formula?
the simplest whole number ratio of atoms in a substance
Steps of the empirical formula
1) calculate the amount in moles of each of the elements present.
2) work out ratio of the elements present
3) Then calculate the molecular formula.
Why do equations need to be balanced?
they need to be balanced in order to remain true with the basic law that atoms cannot be created or destroyed in a reaction, they are only arranged.
Acid-base neutralisation
When an acid and base(chemical opposites) react two compounds are formed. salt and water
Thermal Decomposition
A compound being heated to a high temperature then the breakdown into two or more products occur
acid/metal reaction
They produce the same products. Salt and hydrogen gas. lit splint, squeaky pop as hydrogen ignites.
acid/carbonate reaction
will react similar way as an acid and base, however the carbonate will produce carbon dioxide.
precipitation reaction
two aqueous equations will react to produce an insoluble solid
combustion reaction
In order for anything to burn, oxygen is required. This will produce carbon dioxide and water.
What is the relationship between reactions called?
Stoichiometry
Stoichiometry Steps
1) Calculate the moles
2) calculate the ratio to balance it
3) Rearrange the formulae
The ideal gas law
This law describes how gases would behave at different temperatures and pressure.
Units of pressure, volume and temperature.
pressure= pascals volume= cubic metres temperature= kelvin
With an acid base titration, what will be used to indicate the end point.
An indicator
What do indicators do? as they are special chemicals.
They change colour when they are at a different pH
What will indicate rapid changes?
titration curve.
Equivalence Point
the point in a titration where the volume of one solution exactly matches the volume of the other solution.
Titration calculation steps e.g. nitric acid
1) calculate the number of moles.
2) calculate the amount of moles used
3) convert the volume of titration reading in dm3
4) Calculate the concentration moles/volume
