What is concentration?
Concentration is the measurement unit of the amount of solute present in known solution amounts.
The terms’ solute’ and ‘solution’ are often used in a liquid sample. The actual concentration units depend on how the amounts of solute and solution are measured. The most common units of concentration are list in below,
| NAME | UNIT | SYMBOL |
|---|---|---|
| Molarity | Moles solute/litres solution | M |
| Formality | Number FWs solute/liters solution | F |
| Normality | Numbers Ews solute/liters solution | N |
| Molality | Moles solute/kg solvent | m |
| Weight % | g solute/100 g solution | %w/w |
| Volume % | mL solute/100 ml solution | %v/v |
| Parts per million | g solute/106 g solution | ppm |
| Parts per billion | g solute/109 g solution | Ppb |
| Weight-to-volume % | g solute/10 mL solution | %w/v |
MOLARITY
What is Molarity?
The number of moles of solute per liter of solution is known as Molarity. Molarity is denoted as M.
Or The concentration of a particular chemical species in solution.
For example, dissolving 0.1 mol of NaCl in 1 L of water gives a solution containing 0.1 mol of Na+ and 0.1 mol of Cl–. The Molarity of NaCl is zero; there is no undissociated NaCl in the solution. The solution, instead, is 0.1 M in Na+ and 0.1 M in Cl–.
FORMALITY
What is formality?
The number of moles of solute, regardless of chemical form, per litre of solution. Formality is denoted as F. or A substance’s total concentration in solution without regard to the specific chemical form. The formality symbol is F.
NORMALITY
What is Normality?
The number of equivalents of solute per litre of solution is called Normality. Normality is denoted as N. or Normality makes use of the chemical equivalent, which is the amount of one chemical species reacting stoichiometrically with another chemical species.
The number of equivalents n is based on a reaction unit, which is the part of the chemical species involved in a reaction. In a precipitation reaction, for example, the reaction unit is the charge of the cation or anion involved in the reaction;
n = 2 for Pb+2 and n =1 for I–.
What is equivalent?
The moles of a species can denote one unit.
Molality
What is molality?
The number of moles of solute per kilogram of solvent. Molality is denoted as m.
Using the solvent mass in place of its volume makes the resulting concentration independent of temperature.
Weight, volume and Weight-to-volume Ratios
Weight percent (%w/w), volume percent (%v/v) and weight-to-volume percent (%w/v) express concentration as units of solute per 100 units of the sample.
For example, A solution in which a solute has a concentration of 23% w/v contains 23g of solute per 100 ml solution.
PARTS PER MILLION AND PARTS PER BILLION
Parts per million (ppm) and parts per billion (ppb) are the mass ratios of grams of solute to one million or one billion grams of sample, respectively.
For example, steel that is 450 ppm Mn contains 450 µg of Mn for every gram of steel. If we approximate the density of an aqueous solution as 1.00 g/mL, then solution concentrations can be expressed in parts per million or parts per billion using the following relationship.
