The mole Flashcards
Define amount of substance
The quantity whose unit of the mole, used as a means of counting any species such as atoms, ions, and molecules
Define mole
The amount of substance containing as many elementary particles as there are carbon atoms in exactly 12g of the carbon-12
Define Avogadro’s constant
The number of atoms per mole of the carbon-12 isotope
Define Molar Mass
The mass per mole of a substance
What are the units for molar mass?
g per mole
Define empirical formula
The simplest whole number ratio of atoms of each element present in a compound
Define molecular formula
The actual number of each element present in a molecule
Define anhydrous
containing no water molecules
Define hydrated
A crystalline compound containing water molecules
Define water of crystallisation
Water molecules that are bonded into the crystalline structure of a compound
What does EMMA stand for?
Equation
Moles known
Moles wanted
Answer
Define concentration
The amount of solute in mol dissolved per dm3 of solution
Using volume, how can moles be calculated?
no. moles = concentration x volume
Give a suitable indicator for titration reactions
Phenolphthalein
What is the molar gas volume at RTP?
24.0 dm3 per mol
How can the no. particles be calculated?
No. mol x Avogadro constant
Define standard solution
A solution whose exact concentration is known
Give the formula for calculating concentration
c=n/v
Which piece of equipment is used to make up a standard solution?
A volumetric flask
How are burettes read?
to the nearest half division
Why do you repeat your titration until you get concordant results?
To ensure with confidence that the exact drop which changes the indicator’s colour is found
What should a titration begin with?
A rough titration
Why are rough titrations carried out?
To give you a rough idea of the volume of solution which changes the indicator colour
Are rough titrations included in titration calculations?
No
How do you calculate volume of a gas at rtp?
No. mols x molar gas volume
What is molar gas volume?
The volume per mole of gas molecules at a stated temperature and pressure
What conditions make rtp?
- about 20 degrees Celsius
- 101 KPa or 1 atm of pressure
What is the ideal gas law?
pV= nRT
In the ideal gas law what is pressure measured in?
pascals
In the ideal gas law what units are used for volume?
m cubed
In the ideal gas law what units are used for temperature?
K (kelvin)
What is the gas constant?
8.314
What are the units for the ideal gas constant?
pascals per m cubed per kelvin per mol
How do you convert between Celcius and kelvin?
+273
How do you convert from dm cubed to m cubed?
/1000
How do you convert from kPa to Pa?
x 1000
What is the number of atoms in one mol of carbon dioxide?
1.8 x 10 to the 24
There are 3 atoms in CO2 and therefore avogadro constant should be multiplied by 3
How can random error in a titration be reduced?
- repeat titration until concordant results are achieved
- calculate a mean from the concordant results
