States of Matter, Moles and Elements Flashcards
Solid, Liquid. Gas, Aqueous
(s), (l), (g), (aq)
Calculating Mr
Sum of all atoms present: E.g. H2O
2 x 1 + 16 = 18
Mole:
The unit for amount of a substance
Formula for Moles:
Moles = Mass/Mr
%yield
actual amount of product/theoretical amount of product
Empirical Formula:
The simplest whole number ratio between atoms/ions in a compound
E.g. Pentene C5H10 -> CH2
Molecular Formula:
The actual number of atoms of each type of element in a molecule
Calculating Empirical Formula
- Put symbols for each element at top of page
- Underneath, write masses of each element combining.
- Divide by their relative atomic mass
- Divide all the numbers by the smallest of these numbers to give a whole number ratio
- Use this to give the empirical formula
(If ratio is 1:1.5 multiply by 2, 1:1.33 x 3, 1:1.25 x 4)
Calculating Molecular Formula
- Calculate mass of empirical formula
- Find out the number of times the relative mass of the empirical formula goes into the Mr of the compound
- Multiply the empirical formula by this number
Formula for Moles (in solution):
Moles (mol) = concentration (mol/dm^3) x volume (dm^3)
cm^3 to dm^3
divide by 1000
1 Faraday
96500
Volume of 1 mole of gas at rtp
24dm^3
Solute definition
The substance being dissolved
Solvent definition
The liquid in which the substance is being dissolved
Solution definition
The liquid formed (solute + solvent)
Saturated solution definition
A solution into which no more solute can be dissolved
Solubility definition
The maximum mass of a solute that dissolves in 100g of solvent
solubility = mass of solute/mass of solvent x 100
Element
A substance made up of only one type of atom
Compound
A substance that contains two or more elements chemically joined together in fixed proportions
Mixture
Different substances in the same space, but not chemically combined
Simple distillation
Used to separate a liquid from a solution
E.g. separating water from salt water
The salt water is boiled; the water vapour condenses back into a liquid when passed through the condenser. The salt is left behind in the flask
Fractional distillation
Used to separate a mixture of different liquids with different boiling points
Using a thermometer to monitor the temperature of the fractionating column, by keeping it at a specific temperature, only one liquid boils and its vapour travels up the column, through the condenser and condenses back into a liquid
Filtration
Used to separate an insoluble solid from a liquid
E.g. separating sand from a mixture of sand and water
The mixture is poured into the filter paper; the sand does not pass through and is left behind as residue, but the water passes through and is collected in the conical flask (filtrate)
Crystallisation
Gently heat solution in an evaporating basin to evaporate some of the water;
Until crystals form on a glass rod (shows that a hot saturated solution has formed);
Leave to cool and crystallise;
Filter to remove the crystals;
Dry by leaving in a warm place
Paper chromatography
Used to separate parts of a mixture into their components
E.g. different dyes in ink can be separated
A base line is drawn in pencil (so it doesn’t run/smudge like ink)
A sample/spot of ink is placed on the base line
The paper is lowered into the solvent
!! base line must sit above solvent level (or the ink would dissolve in the solvent)
The solvent is absorbed into the paper and rises up, carrying the dyes with it
Each dye moves up the paper at different rates depending on their solubility
Higher solubility = travel further
Rf value
Rf = Distance of dye from baseline / Distance of solvent front from baseline
Always between 0 and 1
