Quantitative Chemistry Flashcards
What is the conservation of mass?
In a chemical reaction the total mass of the products is equal to the total mass of the reactants because no atoms are lost or made.
What is the relative atomic mass of an element?
The relative mass of the atoms compared with the mass of a carbon-12 atom.
How do you calculate the relative formula mass (Mr)?
- Work out how many atoms of each element there are in the chemical formula
- Add together the Ar values for all the atoms of each element present
Describe the differences between closed and non-enclosed systems.
- No substances can enter or leave a closed system but they can in a non-enclosed system.
Is a neutralisation reaction a closed or non-enclosed system?
Closed because all the products and reactants stay in the beaker.
What are the two ways of estimating uncertainty.
- Resolution (for a thermometer with a mark every 1.0C, the uncertainty is +- 0.5)
- Calculating an average / calculating the range (the mean +- half the range)
What is the formula for calculating concentration?
Concentration = mass of solute / volume
How do you convert from cm3 to dm3?
Divide by 1000.
How can concentration be increased?
- Dissolving more solute in a given volume of a solution so increasing the mass of the solute
- Allowing some of the solvent to evaporate so decreasing the volume.
What is a mole?
A unit (mol)
One mole of a substance contains the same number of particles as one mole of any other substance
What is the Avogadro constant?
6.02 x 10^23
The number of atoms, molecules or ions in one mole of a substance.
How do you calculate the number of particles?
Number of particles = Avogadro constant × the amount of substance in mol
How do you calculate amounts in moles?
Amount = mass / relative atomic mass
When does a reaction end?
When one of the reactants has been completely used up - the other reactant has nothing to react with so is left over.
What is the limiting reactant?
The one that gets all used up.
