Explain the use of preparing standard solutions and titrations?
You use a standard solution to determine the concentration of the analyte during a titration.
A standard solution is a solution containing a precisely known concentration of a primary standard.
A primary standard should be a solid with a known formula and a purity of 99.98 %. It must also be stable in air and water-soluble.
Sodium carbonate is a common primary standard base. It is used to prepare standard solutions for the titration of acids.
Sodium carbonate (13.25 g) was dissolved in about 150 mL of deionized water in a beaker. The solution was transferred with appropriate washings into a 250 mL volumetric flask. The volume of water was made up to the mark, and the solution was thoroughly shaken to ensure complete mixing.
A 25.00 mL volume of the sodium carbonate solution was pipetted into a conical flask. Methyl orange indicator was added.
The sample required 24.65 mL of a hydrochloric acid solution to completely neutralize it.
Calculate the molarity of the hydrochloric acid.
Step 1. Calculate the moles of Na₂CO₃.
Moles of Na₂CO₃ = 13.25 g Na₂CO₃ ×
Step 2. Calculate the molarity of the Na₂CO₃ solution.
Step 3. Calculate the moles of Na₂CO₃ in the aliquot.
Moles of Na₂CO₃ = 0.02500 L soln ×
Step 4. Write the balanced chemical equation for the reaction.
Na₂CO₃ + 2HCl → 2NaCl + H₂CO₃
Step 5. Calculate the moles of HCl.
Moles of HCl = 0.012 501 mol Na₂CO₃ ×
Step 6. Calculate the molarity of the HCl.