Concentration
Contents
Key Stage 2
Meaning
Concentration is how dilute or concentrated a solution is.
About Concentration
- When orange juice is added to water if there is a lot of water but not much orange juice then the solution is dilute. If there is a lot of orange juice, but very little water then it is concentrated.
Key Stage 3
Meaning
Concentration is the ratio of a solute to a solvent.
About Concentration
- The more solute in a solution the higher the concentration.
- The more solvent in a solution the lower the concentration.
- Concentration can have several units but the most common one used in science is Molarity (M).
Key Stage 4
Meaning
Concentration is the ratio of the mass of solute to the volume of solvent.
About Concentration
- Concentration can be measured in g/dm3 or mol/dm3 (Molarity).
- When calculating concentration in g/dm3 the mass of the solute is measured in grams and the volume of solvent is measured in decimetres cubed.
- When calculating concentration in mol/dm3 the amount of solute is measured in Moles by finding the mass and the relative formula mass of the chemical to find out the number of moles and the volume of solvent is measured in decimetres cubed.
Equation
Concentration by Mass
concentration (g/dm3) = \(\frac{mass (g)}{volume (dm^3)}\)
Where:
Concentration by Moles
concentration (g/dm3) = \(\frac{Moles (mol)}{volume (dm^3)}\)
Where:
- Moles = The number of moles of the solute. Found by dividing the mass in grams by the relative formula mass.
- volume = The volume of solvent.
Calculating Concentration
Concentration by Mass
| 117g of NaCl is dissolved in 0.5dm3 of water. Calculate the concentration in g/dm3. | 28g of KOH is dissolved in 100ml of water. Calculate the concentration in g/dm3. | 73g of HCl is dissolved in 400ml of water. Calculate the concentration in g/dm3. |
|
State the mass in grams and the volume in dm3: mass = 117g volume = 0.5dm3 |
State the mass in grams and the volume in dm3: mass = 28g volume = 100ml The volume must be converted into dm3 from ml. volume in dm3 = (volume in ml)/1000 volume = 0.1dm3 |
State the mass in grams and the volume in dm3: mass = 73g volume = 400ml The volume must be converted into dm3 from ml. volume in dm3 = (volume in ml)/1000 volume = 0.4dm3 |
|
Calculate the Concentration: concentration (g/dm3) = \(\frac{mass (g)}{volume (dm^3)}\) concentration = \(\frac{117}{0.5}\) concentration = 234g/dm3 |
Calculate the Concentration: concentration (g/dm3) = \(\frac{mass (g)}{volume (dm^3)}\) concentration = \(\frac{28}{0.1}\) concentration = 280g/dm3 |
Calculate the Concentration: concentration (g/dm3) = \(\frac{mass (g)}{volume (dm^3)}\) concentration = \(\frac{73}{0.4}\) concentration = 182.5g/dm3 |
Concentration as Molarity
| 117g of NaCl is dissolved in 0.5dm3 of water. Calculate the concentration in g/dm3. | 28g of KOH is dissolved in 100ml of water. Calculate the concentration in g/dm3. | 73g of HCl is dissolved in 400ml of water. Calculate the concentration in g/dm3. |
|
Find the number of moles. mass = 117g Relative Formula Mass = 58.5g Number of Moles of a Compound = (Mass of compound)/(Relative Formula Mass of compound) Number of Moles = \({\frac{m}{M_r}}\) Number of Moles = \({\frac{117}{58.5}}\) Number of Moles = 2mol
|
State the mass in grams and the volume in dm3: Find the number of moles. mass = 28g Relative Formula Mass = 56g Number of Moles of a Compound = (Mass of compound)/(Relative Formula Mass of compound) Number of Moles = \({\frac{m}{M_r}}\) Number of Moles = \({\frac{28}{56}}\) Number of Moles = 0.5mol |
Find the number of moles. mass = 73g Relative Formula Mass = 36.5g Number of Moles of a Compound = (Mass of compound)/(Relative Formula Mass of compound) Number of Moles = \({\frac{m}{M_r}}\) Number of Moles = \({\frac{73}{36.5}}\) Number of Moles = 2mol |
|
volume = 0.5dm3 |
volume = 100ml The volume must be converted into dm3 from ml. volume in dm3 = (volume in ml)/1000 volume = 0.1dm3 |
volume = 400ml The volume must be converted into dm3 from ml. volume in dm3 = (volume in ml)/1000 volume = 0.4dm3 |
|
Calculate the Concentration: concentration (mol/dm3) = \(\frac{Moles (mol)}{volume (dm^3)}\) concentration = \(\frac{117}{0.5}\) concentration = 234g/dm3 |
Calculate the Concentration: concentration (mol/dm3) = \(\frac{Moles (mol)}{volume (dm^3)}\) concentration = \(\frac{28}{0.1}\) concentration = 280g/dm3 |
Calculate the Concentration: concentration (mol/dm3) = \(\frac{mass (g)}{volume (dm^3)}\) concentration = \(\frac{73}{0.4}\) concentration = 182.5g/dm3 |