Unit 2 Learning aim A: Undertake titration and colorimetry to determine the
concentration of solutions.
In this assignment I undertook various experiments in both titration and colorimetry to determine
the concentration of solutions. In my first experiment, I prepared a standardized solution of
sodium carbonate (Na2CO3) to find the concentration of dilute hydrochloric acid by titration
(standardising hydrochloric acid) using phenolphthalein and methyl orange indicator.
Afterwards, I used the standardised hydrochloric acid (from my first experiment) to determine
the unknown concentration of sodium hydroxide (NaOH) by volumetric pH titration of the
hydrochloric acid using a calibrated pH meter. These titration experiments enabled me to
calculate the concentration of hydrochloric acid and sodium hydroxide. I then carried out a
colorimetry experiment to enable me to calculate the concentration of copper sulphate.
Experiment 1: To standardise a solution of hydrochloric acid using a primary standard,
anhydrous sodium carbonate, to find the concentration of dilute hydrochloric acid by
titration.
Hypothesis: From the equation, Na2 CO 3+2 HCL−−→2 NaCl+ H 20+CO 2, there is a 1:2
mole ratio of acid:base. From this I predict that the volume of hydrochloric acid used should be
twice the volume of 25ml of sodium carbonate solution at the point of neutralisation.
Introduction: In this experiment I carried out standardization, which in my case is the process
of determining the exact concentration (molarity) of a sodium carbonate solution. Afterwards, I
carried out titration, which is the slow addition of one solution of a known concentration (sodium
carbonate) to a known volume (of HCL) with an unknown concentration until the reaction
reaches neutralisation, indicated through a colour change.
From standardising the hydrochloric acid, the reaction between sodium carbonate and
hydrochloric acid takes place in two stages:
(1) Na 2 CO 3+ HCL−−→2 NaHC 03+ NaCl
(2) 2 NaHCO 3+2 HCL−−→2 NaCl+3 CO 2+ H 20
In stage 1, phenolphthalein indicator is used to respond to the pH change associated with the
formation of sodium hydrogencarbonate, NaHCO3.
In stage 2, methyl orange is used to respond to the pH change associated with the final
formation of sodium chloride, NaCl.
concentration of solutions.
In this assignment I undertook various experiments in both titration and colorimetry to determine
the concentration of solutions. In my first experiment, I prepared a standardized solution of
sodium carbonate (Na2CO3) to find the concentration of dilute hydrochloric acid by titration
(standardising hydrochloric acid) using phenolphthalein and methyl orange indicator.
Afterwards, I used the standardised hydrochloric acid (from my first experiment) to determine
the unknown concentration of sodium hydroxide (NaOH) by volumetric pH titration of the
hydrochloric acid using a calibrated pH meter. These titration experiments enabled me to
calculate the concentration of hydrochloric acid and sodium hydroxide. I then carried out a
colorimetry experiment to enable me to calculate the concentration of copper sulphate.
Experiment 1: To standardise a solution of hydrochloric acid using a primary standard,
anhydrous sodium carbonate, to find the concentration of dilute hydrochloric acid by
titration.
Hypothesis: From the equation, Na2 CO 3+2 HCL−−→2 NaCl+ H 20+CO 2, there is a 1:2
mole ratio of acid:base. From this I predict that the volume of hydrochloric acid used should be
twice the volume of 25ml of sodium carbonate solution at the point of neutralisation.
Introduction: In this experiment I carried out standardization, which in my case is the process
of determining the exact concentration (molarity) of a sodium carbonate solution. Afterwards, I
carried out titration, which is the slow addition of one solution of a known concentration (sodium
carbonate) to a known volume (of HCL) with an unknown concentration until the reaction
reaches neutralisation, indicated through a colour change.
From standardising the hydrochloric acid, the reaction between sodium carbonate and
hydrochloric acid takes place in two stages:
(1) Na 2 CO 3+ HCL−−→2 NaHC 03+ NaCl
(2) 2 NaHCO 3+2 HCL−−→2 NaCl+3 CO 2+ H 20
In stage 1, phenolphthalein indicator is used to respond to the pH change associated with the
formation of sodium hydrogencarbonate, NaHCO3.
In stage 2, methyl orange is used to respond to the pH change associated with the final
formation of sodium chloride, NaCl.
