Solution | Concentration Terms#
Concentration Terms#
- Concentration Terms are used to express the amount of solute dissolved in a solvent.
- There are different concentration terms like mass percentage, volume percentage, mass by volume percentage, parts per million, molarity, molality, mole fraction
- We will discuss each one of them in detail.
Mass Percentage(w/w)#
Mass percentage of a component of a solution is defined as:
If 10 gram sugar is present in 90 gram water, find its mass percentage.
Here, the mass of solution is (10+90) grams = 100 grams.
Volume Percentage(v/v)#
Volume percentage of a component of a solution is defined as:
If 10 ml sugar is present in 90 ml water, find its volume percentage.
Here, the volume of solution is (10+90) ml = 100 ml.
Mass by Volume Percentage(w/v)#
Mass by volume percentage of a component of a solution is defined as:
If 10 grams sugar is present in 100 ml solution, find its volume percentage.
Here, the volume of solution is = 100 ml.
Parts per million(ppm)#
- When solute is present in very small amount, we express its concentration in terms of parts per million.
ppm is calculated using the following formula:
where, n = Number of parts of component
and, N = Number of parts of all components of solution
- Parts per million can be expressed as mass to mass, volume to volume and mass to volume.
Parts per billion (ppb)#
parts per billion(ppb) is defined as:
where, n = Number of parts of component
and, N = Number of parts of all components of solution
- Similar to ppm, parts per billion(ppb) is also used when solute is in a very small amount.
Mole Fraction (Χ)#
- For a solution consisting of A as solute and B as solvent, we define mole fraction of A present in the solution as:
where, nA = Moles of A
and, nB = Moles of B
- Similarly, mole fraction of B in the solution is defined as:
- Here, we can see that:
- Similarly, for a solution containing k components, we can write:
Similarly,
And,
Molarity(M)#
- Molarity is defined as number of moles of solute present in one litre of solution.
- Since molarity is dependent on volume, it changes with change in temperature.
Molality(m)#
- Molality is defined as number of moles of solute present in one kilogram of solvent.
- Molality does not change with change in temperature.