Solutions and Gases
Standard solution - A solution of known concentration. Used in titration
Concentration - A measure of how much solute is dissolved in a volume of solvent
● Measured in g/dm3 or mol/dm3
moles∨mass
Concentration =
volume
Working with solutions
I have a solution containing 80g of solute in 1 dm3 of solvent, what is the concentration?
●
80 = 80g/mol
1
I have a solution containing 40 g of sodium hydroxide in 2dm3. What is the concentration in
mol/dm3?
● The question wants the answer is mol/dm3 this time. So first we need to find the
number of moles
● Find the Mr of NaOH
● 23 + 1 + 16 = 40
mass
● Number of moles =
Mr
40
● = 1 mol
40
● This can now be put into the concentration equation
1
● = 0.5mol/dm3
2
How many moles of HCl are there in 25cm3 of a 0.1mol/dm3 solution?
● Volume must be measured in dm3
● So 25cm3 becomes 0.025dm3
moles∨mass
● Next we rearrange ‘concentration = ’ so the result is moles
volume
○ Moles = concentration x volume
● Moles = 0.1 x 0.025
● = 0.0025 moles
Avogadro’s law
● At the same pressure and temperature, equal volumes of gases contain equal
molecules
● At room temperature and pressure one mole of gas occupies 24dm3
● Standard conditions are 25°c and 1 atm pressure
● It is easier to measure the volume of gas than to weigh its mass
Molar gas volume = 24dm3
Standard solution - A solution of known concentration. Used in titration
Concentration - A measure of how much solute is dissolved in a volume of solvent
● Measured in g/dm3 or mol/dm3
moles∨mass
Concentration =
volume
Working with solutions
I have a solution containing 80g of solute in 1 dm3 of solvent, what is the concentration?
●
80 = 80g/mol
1
I have a solution containing 40 g of sodium hydroxide in 2dm3. What is the concentration in
mol/dm3?
● The question wants the answer is mol/dm3 this time. So first we need to find the
number of moles
● Find the Mr of NaOH
● 23 + 1 + 16 = 40
mass
● Number of moles =
Mr
40
● = 1 mol
40
● This can now be put into the concentration equation
1
● = 0.5mol/dm3
2
How many moles of HCl are there in 25cm3 of a 0.1mol/dm3 solution?
● Volume must be measured in dm3
● So 25cm3 becomes 0.025dm3
moles∨mass
● Next we rearrange ‘concentration = ’ so the result is moles
volume
○ Moles = concentration x volume
● Moles = 0.1 x 0.025
● = 0.0025 moles
Avogadro’s law
● At the same pressure and temperature, equal volumes of gases contain equal
molecules
● At room temperature and pressure one mole of gas occupies 24dm3
● Standard conditions are 25°c and 1 atm pressure
● It is easier to measure the volume of gas than to weigh its mass
Molar gas volume = 24dm3
