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A titration calculation
The method for titration calculations is the one you have used for mole calculations already:
Write a balanced equation for the reaction.
Find the number of moles of the known substance.
Use the balanced equation to find the number of moles of the unknown substance.
Work out the mass, concentration or volume of the unknown.
MAVA/MBVB = NA/NB
MA = Molarity of acid in mol/dm3
VA = Volume of the acid in cm3
MB = Molarity of base in mol/dm3
VB = Volume of the base in cm3
NA = Number of moles of acid
NB = Number of moles of base
Example 1: Calculate:
(a) the mass of anhydrous Na2CO3 present in 300cm3 of 0.1M
(b) the number of Na2CO3 particles present in the solution (Na = 23, C = 12, O = 16)
(a) Molarity of the Na2CO3 solution = 0.1 M
Molar mass of Na2CO3 = 23 x 2 + 12 + 16 x 3 = 106g/mol
Concentration (g/dm3) = Molarity x molar mass
0.1 x 106
This means 1000cm3 of 0.1M solution contain 10.6g of Na2CO3
300cm3 of 0.1 M solution will contain: 300 x 10.6 / 1000
= 3.18g of Na2CO3
(b) Number of Na2CO3 particles = molarity x 6.02 x 1023
0.1 x 6.02 x 1023
= 0.602 x 1023
This means 1000cm3 of 0.1 M solution contain 0.602 x 1023 Na2CO3 particles
300cm3 of 0.1M solution contain
Example 2: 20.30cm3 of hydrochloric acid solution was titrated against 25cm3 of 0.1M sodium hydroxide solution. Calculate:
(i) the concentration of the acid in mol/dm3
(ii) the concentration of the acid in g/dm3
Equation of reaction
HCl (aq) + NaOH (aq) ——–> NaCl (aq) + H2O (l)
1 : 1
(i) MA =?, MB = 0.1 M, VA = 20.30cm3, VB = 25cm3, NA = 1, NB = 1
MAVA/MBVB = NA/NB
MA = MBVB NA / VA NB
MA = 0.1 x 25 x 1 / 20.30 x 1
MA = 0.123 mol/dm3
(ii) Molarmass of Acid = 36.5 g/mol, Concentration of Acid in mol/dm3 = 0.123 mol/dm3
Concentration of Acid in g/dm3 = Concentration of Acid in mol/dm3 x Molarmass
= 0.123 x 36.5
= 4.49 g/dm3
Assessment (Post your answer using the Stoplearn.com box below for evaluation and discussion)
Calculate the concentration of the solution if 25g of NaOH is dissolve in 500cm3 of water.
32.30cm3 of hydrochloric acid solution was titrated against 25cm3 of 0.2M sodium hydroxide solution. Calculate: a. the concentration of the acid in mol/dm3 b. the concentration of the acid in g/dm3
If 21.2 g of Calcium Trioxocarbonate were dissolved in 15 g of distilled water at 30oC, calculate the solubility of the solute in mol dm-3.