Acid & Base titrations: MCQ 4

Study Notes

Titration

Acid from the burette is dropped into the conical flask, and the flask is constantly swirled as the acid is added.
Any solution adhering to the sides of the conical flask can be washed down with DI water from a wash bottle.
Acid is added until a colour change occurs, and this is known as the 1ˢᵗ titration.
2 accurate titrations are then carried out to determine the value of the unknown concentration of the acid.

Titration Calculations

Write out titration conclusion
Use ratio from chemical equation to work out moles of unknown solution
Find concentration of unknown using moles & volume
Work out number of moles of known solution

Standardizing Acids

Acids are generally unstable solutions, and their concentrations can vary due to HCl being volatile, HNO₃ being volatile, and H₂SO₄ being hygroscopic.
These acids must be standardized with a base.

Acid & Base Titrations

Indicator used: Methyl Orange
Colour change: Yellow → Peach/Pink
Experiment 1: Standardisation of HCl

Vinegar Titrations

Vinegar contains ethanoic acid
Experiment 2: Vinegar vs. NaOH
Indicator used: Phenolphthalein
Colour change: Pink → Colourless
Steps in solving vinegar titration questions:
- Work out the concentration of titrated vinegar
- Take account of the dilution factor
- Convert g/L into % w/v
- Calculate the concentration of ethanoic acid in the original vinegar

Experiment 3: Water of Crystallisation

Some substances involved in neutralisation reactions contain water in their crystalline structure
Sodium carbonate can either be anhydrous or hydrated
Hydrated sodium carbonate is represented as Na₂CO₃.xH₂O
By titrating this base against a standardised acid, we can work out both the value of x and the % water of crystallisation in the structure

Solving Water of Crystallisation Q’s

Solve for the concentration of the base
Convert M → g/L…….× Mr
Use actual volume to get mass of anhydrous base
Find the % water of crystallisation

Description

Learn about the step-by-step process of titration, including the addition of acid, swirling, and washing of the conical flask, as well as calculations and conclusions. Test your understanding of this fundamental chemistry concept.