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Acid and Base Chemistry - Coggle Diagram
Acid and Base Chemistry
Quantitative Analysis
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Titration are used to calculate the unknown concentration of the acid because it is not a primary standard
A titration is a volumetric procedure in which a primary standard is used to determine the concentration of a solution of unknown concentration.
Clean a conical flask and a 25 mL pipette with water. Rinse the pipette with the standard sodium carbonate solution. Fill the pipette with the sodium carbonate solution and transfer the solution to the conical flask.
Clean a 50 mL burette with water and then rinse the burette with the acid solution. Discard the washings and fill the burette with the acid (e.g. HCl) solution.
Add four drops of the appropriate indicator (e.g. methyl orange) to the flask and add the acid to the flask until the indicator turns from yellow to orange. The volume of acid is recorded. This volume (called the titre) is used to calculate the acid concentration
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Reminders
Pipette contains standard solution, burette contains titrant of known concentration, conical flask contains analyte of unknown concentration.
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Coat apparatus in deionised water before adding substance gets rid of impurities. Rinsing burette and pipette with solution ensures the solution is not diluted.
Don’t attach the bubble thing when it is connected to retort stand. Indent the buddle before attaching it by holding the burette up the top. Hold S to suck water in and E to empty – make sure the bottom of the meniscus is on the line.
Conductivity Graphs
Equivalence point: describes the neutralisation point where all hydrogen ions are neutralised by hydroxide ions. Graphically it is the longest section on a titration curve where the pH changes, however the volume of the titrant in the pipette doesn’t change.
Titrations Curves
- Alternative to testing the neutralisation of a solution is through a conductivity probe. Conductivity of electricity in solution is dependent on the concentration of ions in that solution, hence this is used to measure that
- more ions = the more conductive solution
- When a solution is very basic or very acidic there will be loads of hydrogen or hydroxide ions floating around
- Conductivity will decrease until it reaches a minimum where ions of each are equal, then increase again as you are continuously adding ionising solutions
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pKa Calculations
- pKa is defined as pKa = –log10Ka
- The larger the pKa , the weaker the acid
Buffers
- resists large changes in pH on the addition of small quantities of strong acids or bases
- greatest buffering effect is obtained if the buffer solution contains equimolar concentrations of the weak acid and its conjugate base
- pH for buffer (acid + conjugate base) * WA/WB + SALT
- Natural buffers used to
maintain blood pH
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