Concentrations is measurements of the dissolved of solutes dissolves in a given volume of solvents when solution is formed.
Important Definition for Acids
Monoprotic acid (monobasic acid) is an acid which produce one mole of H+ ion when one mole of the acid ionise in water.
Example of monoprotic acid
Hydrochloric acid, HCl
Nitric acid, HNO3
Ethanoic acid, CH3COOH .
Polyprotic acids
Diprotic acid (dibasic acid) is an acid which produce two moles of H+ ions from one mole of the acid in water.
Example of diprotic acid
Sulphuric acid, H2SO4
Carbonic acid, H2CO3
Chromic acid, H2CrO4
Ethanedioic acid / Oxalate acid, H2C2O4
Triprotic acid (tribasic acid) is an acid which produce three moles of H+ ions from one mole of the acid in water.
Example of triprotic acid
Phosphoric acid, H3PO4
Citric acid, C6H8O7
Concentration of Acids and Alkalis
Relationship between Number of Moles with Molarity and Volume of a Solution
Preparation of Standard Solutions
Preparation of a Solution by Dilution Method
Relationship between pH Values and Molarities of Acids or Alkalis
Important Definition for Acids
Monoprotic acid (monobasic acid) is an acid which produce one mole of H+ ion when one mole of the acid ionise in water.
Example of monoprotic acid
Hydrochloric acid, HCl
Nitric acid, HNO3
Ethanoic acid, CH3COOH .
Polyprotic acids
Diprotic acid (dibasic acid) is an acid which produce two moles of H+ ions from one mole of the acid in water.
Example of diprotic acid
Sulphuric acid, H2SO4
Carbonic acid, H2CO3
Chromic acid, H2CrO4
Ethanedioic acid / Oxalate acid, H2C2O4
Triprotic acid (tribasic acid) is an acid which produce three moles of H+ ions from one mole of the acid in water.
Example of triprotic acid
Phosphoric acid, H3PO4
Citric acid, C6H8O7
Concentration of Acids and Alkalis
- Quantity of solute can be measured in grams or moles: g dm-3 or mol dm-3.
- Concentration (g dm-3) = mass of solute (g) / volume of solution (dm3)
- Concentration (mol dm-3) = number of moles of solute (mol) / volume of solution (dm3)
Relationship between Number of Moles with Molarity and Volume of a Solution
- Molarity (mol dm-3) = number of moles of solution (mol) / volume of solution (dm3)
- M = molarity of solution (mol dm-3), V = Volume of solution (dm3), n = Number of moles of solute (mol)
- M = n/V
Preparation of Standard Solutions
- Standard solution = a solution in which its concentration is accurately known.
- Standard solution is prepared by using volumetric flask with a fixed volume (100 cm3, 200 cm3, 250 cm3, 500 cm3 and 1000 cm3)
Preparation of a Solution by Dilution Method
- Dilution = a process of diluting a concentrated solution by adding a solvent (water) to obtain a more diluted solution.
- The concentration of the solution decreases after dilution.
- The number of moles of solute in the solution remains unchanged after dilution.
- (MaVa) / 1000 = (MbVb) / 1000
- Ma = Initial molarity of solution, Mb = Final molarity of solution, Va = Initial volume of solution and Vb = Final volume of solution
Relationship between pH Values and Molarities of Acids or Alkalis
- pH values depends on degree of dissociation and molarity / concentration of hydrogen ions, H+/ hydroxide ions, OH- in the solution.
- The higher the molarity of a strong acid, the lower is its pH value.
- The higher the molarity of a strong alkali, the higher is its pH value.
- The molarity of an acid can be changed when (i) water is added, (ii) an acid of different concentration is added and (iii) an alkali is added.