This is the theory section of acid-base titrations.
Experiments make up the majority of this section.
1 molar = 1 mole per litre e.g. 1 mole Na2CO3 = 106g/L : 0.1 molar = 1.6g/L
Concentration is the amount of solute in a specified amount of solution e.g. moles per litre or grams per litre
Ways of Expressing Concentration
- Percentage weight per volume (w/v) e.g. 3% NaCl solution = 3g NaCl in 100cm³ solution
- Percentage volume per volume (v/v) e.g. 3% alcohol solution = 3cm³ alcohol in 100cm³ solution
- Percentage weight per weight (w/w) e.g. 3% sugar solution = 3g sugar in 100g solution
- Parts per million (p.p.m.) e.g. 2 p.p.m. solution has 2mg substance per litre
Standard solution a solution whose concentration is accurately known
Primary standard a water-soluble substance that is stable and available in pure form
Formula for Titration Problems
V1 x M1 = V2 x M2
n1 n2 Where V=volume, M=molarity, n=moles of solution present
If 20cm³ of 0.3 molar NaOH are neutralised by 25cm³ of H2SO4 solution, find the concentration of H2SO4 in (i) moles/L (ii)g/L according to the equation 2NaOH + H2SO4 >>> Na2SO4 + 2H2O
V1=25cm³
M1=M1 n1=1
V2=20cm³
M2=0.3 n2=2
25 x M1 = 20 x 0.3
1 2
M1 = 0.12 molar
(i) 0.12 moles/litre
(ii) 0.12 x 98 g = 11.76 g/litre
