An acid base titration is the determination of acid or base concentrations by neutralizing acids or bases with known acid or base of concentration. This allows for a quantitative analysis of unknown acid or acid base concentrations. It makes use of the neutralization reaction that occurs between acids and bases. p K a and K a (acid constants) can also be determined from the pH titration graph.
Acid-base titration can also be used to find percent of chemical purity.
Video Acid-base titration
Alkalimetry dan acidimetry
Alkalimetry and acidimetry are a kind of volumetric analysis in which the fundamental reaction is a neutralization reaction. Alkalimetry is the use of special analytic acid-base titration to determine the concentration of the basic substance (identical with the base). Acidimetry, sometimes spelled acidometry, is the same concept of a special analytic acid-base titration, but for an acidic substance.
Maps Acid-base titration
Tools
The main equipment used in the titration is:
- Buret
- White tiles - used to see color changes in solutions
- Pipette
- the pH indicator (used varies depending on the reactant)
- Bottle of erlenmeyer/conical flask
- Titrant or titrator (standard solution of known concentration, commonly aqueous sodium carbonate)
- Analyze or titrand (concentration solution unknown)
Method
Before starting the titration, an appropriate pH indicator should be selected. The equivalent point of the reaction, the point at which the amount of reactant equivalent reacts, will have a pH that depends on the relative strength of the acid and base used. The equivalence point PH can be estimated using the following rules:
- Strong acids will react with strong bases to form a neutral solution (pH = 7).
- Strong acids will react with weak bases to form acid solution (pH & lt; 7).
- Weak acids will react with strong bases to form the basic solution (pH & gt; 7).
When the weak acid reacts with a weak base, the equivalence point solution will be the base if the base is stronger and acid if the acid is stronger. If both have the same power, then the pH equality will be neutral. However, weak acids are not often titrated to weak bases because the color changes indicated by the indicator are often rapid, and therefore it is very difficult for the observer to see the discoloration.
The point at which the color changing indicator is called the end point. Suitable indicators should be selected, preferably those that will experience discoloration (end points) close to the equivalence point of the reaction.
First, the burette should be rinsed with standard solution, pipettes with unknown solution, and a conical flask with distilled water.
Second, the known volume of the unknown concentration solution must be taken with a pipette and placed into a conical flask, together with a small number of selected indicators.
The known solution should then be left out of the burette, into a conical flask. At this stage we want a rough estimate of the number of solutions needed to neutralize an unknown solution. The solution must be removed from the burette until the indicator changes color and the value on the burette should be recorded. This is the first (or rough) titration volume and must be excluded from any calculation.
At least three more titles should be performed, this time more accurately, taking into account roughly where the end point will occur. The initial and final readings on the burette (before starting the titration and at the end point, respectively) should be recorded. Reducing the initial volume of the final volume will result in the number of titrant used to reach the end point. The end point is reached when the indicator changes color only permanently.
Acid-base titration is performed with bromothymol blue indicator, when strong titration of acids - strong titration, phenolphthalein indicator in weak acid - strong base reaction, and methyl orange indicator for strong acid - weak base reaction. If the base of the scale, ie pH & gt; 13.5, and acid has a pH & gt; 5.5, then the Alizarine yellow indicator can be used. On the other hand, if the acid is out of scale, ie pH & lt; 0.5, and base has pH & lt; 8.5, the Thymol Blue indicator can be used.
Weak acid titration
The pH of a weak acid solution titrated with a strong base solution can be found at different points along the path. These points fall into one of four categories:
- initial pH
- pH before the equivalence point
- pH at the equivalent point
- pH after the equivalent point
for a more rigorous calculation, using the RICE chart is required. Actually the equation below is a simplified RICE chart.
Single formula
The titration process creates solutions with compositions ranging from pure acids to pure bases. Identifies the pH associated with any stage in a relatively simple titration process for monoprotic acids and bases. The presence of more than one acid or group of bases makes this calculation difficult. Graphical methods, such as equiligraph, have long been used to account for the interplay of combined equilibria. This graphical solution method is easy to implement, but rarely used.
See also
- Titration
- Titration curve
- Point equality
- The acid dissociation constant
- Acid-base reaction
- Henderson-Hasselbalch's Equation
References
External links
- Graphical methods for solving acid-base problems, including titration
- Image and numeric solvers for common acid-base issues - Software Programs for phones and tablets
Source of the article : Wikipedia
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