Volumetric analysis revision

What is the purpose of Volumetric Analysis?

• The purpose of volumetric analysis is to determine the concentration of an standard solution. Therefore the process is quantitative.

• The purpose of volumetric analysis is to determine the concentration of an known solution. Therefore the process is quantitative.

• The purpose of volumetric analysis is to determine the concentration of an standard solution. Therefore the process is qualitative.

• The purpose of volumetric analysis is to determine the concentration of an unknown solution. Therefore the process is quantitative.

What is the purpose of the indicator?

• To change colour

• To change colour and therefore identify the endpoint of the reaction

• It is a weak base and therefore will turn into its conjugate acid

• An example is phenolphthalein

What is a titre?

• The initial volume in the burette

• The initial volume in a conical flask

• A titre is the volume delivered by the burette

• The volume that is dissolved in the volumetric flask

What is the difference between the end point and the equivalence point of a reaction?

• The end point is the point at which the colour changes and it is one drop before the equivalence point. The equivalence point is the point at which at which exact stoichiometric ratios of the reactants have reacted in the reaction.

• The equivalence point is the point at which there is a colour change in the reaction and the end point is the point at which exact stoichiometric ratios of the reactants have reacted in the reaction.

• The endpoint is the point one drop after the equivalence point, which signals the reaction has been completed by a colour change. The equivalence point is the point at which exact stoichiometric ratios of the reactants have reacted in the reaction.

• The end point and equivalence point are viewed as the same on a titration curve and therefore they are the same point

What is a titration curve and what does it measure?

• A titration curve measures the titre volume over time. This can be utilised to calculate the average titre

• A titration curve measures concordant titres. Make sure to eliminate outliers before determining whether a titre is concordant.

• The titration curve measures the pH of the solution in the conical flask over time as the titrant is added from the burette.

• The titration curve measures the pH of the solution in the burette over time as the titrant is added from the conical flask.

What is a standard solution? What is it made from?

• A standard solution is a solution of accurately known concentration. The standard solution is made from dissolving a known amount of titrant from the burette.

• A standard solution if the titrant that is titrated from the burette.

• A standard solution is a primary standard.

• A standard solution is a solution of accurately known concentration. The standard solution is made from dissolving a known amount of primary standard.

Looking at the graph opposite, what reactants could have reacted to give you this titration curve? What indicator could be chosen?

Which of the following requirements are NOT needed for a primary standard to be utilized?

• Accurately known formula

• Stable so it can react with H2O and CO2 in the air

• Low molar mass (to minimise calculation errors)

• High state of purity

What is the name of the solution that the pipette delivers? Does it deliver it to the conical flask or the burette or either?

• The pipette delivers the titre It can deliver the solution into the conical flask only.

• The pipette delivers the aliquot. It can deliver the solution into the burette or conical flask (either).

• The pipette delivers the aliquot. It can deliver the slution into the conical flask only.

• The pipette delivers the titre It can deliver the solution into either the conical flask or the burette

A standard solution of potassium carbonate is made

by adding 1.227 g of K2CO3 to a 250.0 mL volumetric

flask and filling to the mark with water. 20.00 mL

aliquots are taken and titrated against a sulfuric acid

solution, using methyl orange indicator. The average

titre was 22.56 mL of sulfuric acid.

a. Write the equation for the reaction.

b. Calculate the concentration of the K₂CO₃ solution.

c. Calculate the concentration of the sulfuric acid

solution.