Ch. 3.3 : Moles and Volumes Flashcards
What is the equation that links concentration , miles and volumes ?
Moles = concentration x volume
What is concentration ? Units?
The amount of solute , in moles , dissolved in each dm3 of solution. Mol dm^-3
How do you work out how much a certain solution is required to prepare a certain volume of a solution with a known concentration?
- Work out the amount in moles required. Moles = concentration x volume
- Work out the molar mass of the solution with the unknown concentration
- Re arrange moles = mass / molar mass to calculate the mass of the solution
What is molar gas volume ?
The volume per mole of gas molecules at a stated temperature and pressure. Vm.
What is RTP? What is molar gas volume at RTP?
Room temperature and pressure.
This is about 20°C and 101 kPa ( 1 atm)
At RTP, 1 mole of gas molecules has a volume of approximately 24dm3. Therefore molar gas volume = 24 dm^3 mol^-1
How do you link moles, volume and molar gas volume ?
Moles = volume / molar gas volume
What is the ideal gas equation ?
pV = nRT
p = pressure ( Pa) V = volume ( m3) n = moles R = ideal gas constant T = temperature ( K )
How can you rearrange the ideal gas equation to find moles?
n= pV/ RT
What are the assumptions made for the molecules making up an ideal gas?
- random motion
- elastic collisions
- negligible size
- no intermolecular forces
How do you calculate the relative molecular mass of something?
Convert all the quantities to match the ideal gas equation
Use the ideal gas equation to calculate the unknown
Find the molar mass ( using moles = mass / molar mass )
How do you convert from cm3 to m3?
Divide by 1000000
How do you convert from dm3 to m3?
Divide by 1000
How do you convert from °C to K?
+ 273
How do you convert from kPa to Pa?
X 1000
