Physical Chapter 2: Amount of Substance Flashcards
What is Avogadro’s constant?
6.022x10^23
What is a mole?
An avogadro’s constant number of molecules or atoms
What is the formula linking mass, Mr, and Moles?
Moles = Mass/Mr
What is the formula linking concentration, volume, and moles?
Concentration = Mol/Volume
What is the ideal gas equation?
PV=nRT
Pressure = pa
V = m^3
n = number of moles
R = gas constant
T = Kelvin
How do you convert from degrees to Kelvin?
Add 273
How do you convert from cm^3 to dm^3?
Divide by 1000
What is a standard solution?
Any solution you know the concentration of
What can you find out via Titration?
Concentration of an acid or an alkali
What are the steps for a titration?
Use a pipette to measure out a set volume of the unknown solution
Add a few drops of an appropriate indicator
Fill a burette with a standard solution
Do a rough titration to figure out where the end point is
Do an accurate titration - add to within 2cm of the end point then add dropwise until change occurs
Repeat until you have 3 concordant results
Calculate the mean volume of acid used from concordant results
What are appropriate indicators for titrations?
Methyl orange - red in acid & yellow in alkali
Phenolphthalein - colourless in acid & pink in alkali
What is molecular formula?
Shows the actual numbers of each atom in a compound (E.g. C6H12)
What is an empirical formula?
Shows the simplest whole number ratio of each element in a compound (e.g. C6H12 has empirical formula CH2)
How do you calculate empirical formula?
Comparing ratios via either percentage or mass
What is the formula for percentage yield?
(Actual Yield/Theoretical Yield) x100
