U1S2 amount of substance Flashcards
What is a mole
6.022x10^23 particles
How to calculate the number of particles
Number of moles x avogadros constant
How to calculate the number of moles
Mass of substance/mr
How to calculate concentration of a substance
Moles/volume
How to convert from cm cubed to dm cubed
Divide by 1000
What is the ideal gas equation
pV = nRT
What is the stem of a neutralisation reaction
Acid + alkali = salt + water
How do you create a standard solution e.g. sodium hydroxide
- Calculate moles of sodium hydroxide you need and use this to work out mass you need
- Place weighing bottle on digital balance, weigh out required mass and tip into beaker
- Weigh weighing bottle and subtract mass from mass of bottle and solid
- Add distilled water to beaker and stir until all has dissolved
- Tip solution into a 250cm^3 volumetric flask using a funnel
- Rinse beaker, stirring rod and funnel with distilled water and add to flask too
- Top up flask to correct volume and stopper flask
- Calculate exact concentration
What does a titration allow you to do
Find out exactly how much acid is needed to neutralise an alkali and vice versa
How do you carry out a titration
- Start off using a pipette to measure set volume of solution you want to know concentration of and put in conical flask
- Add a few drops of indicator to flask
- Fill a burette with a standard solution of the acid using a funnel
- Do a rough titration first and then do an accurate titration - when within 2cm^3 of end point, slow down
- Work out volume of acid needed to neutralise alkali which is called titre
- Repeat titration until you have three results within 0.1 cm^3 of each other and calculate mean
Examples of indicators and their colours from acid to alkali
- methyl orange, red -> yellow
- phenolphthalein, colourless -> pink
What is an empirical formula
Formula that gives smallest whole number ratio of atoms of each element present
What is a molecular formula
Formula that gives actual number of atoms in a molecule
What is theoretical yield
Mass of product that should be formed in a chemical reaction
How to calculate percentage yield
Actual yield/theoretical yield x 100
What is atom economy
A measure of the proportion of reactant atoms that become part of the desired product
What are the advantages of a high atom economy
-makes more efficient use of raw materials
- less waste to deal with
- more sustainable
How to calculate atom economy
Molecular mass of desired product/molecular mass of all reactants x 100
