Basics of titration

Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyze. Since volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the titrant or titrator is prepared as a standard solution. A known concentration and volume of titrant reacts with a solution of analyte or titrand to determine concentration. The volume of titrant reacted is called titration volume. A typical titration begins with a beaker or Erlenmeyer flask containing a very precise volume of the analyte and a small amount of indicator(such as phenolphthalein) placed underneath a calibrated burette or chemistry pipetting syringe containing the titrant. Small volumes of the titrant are then added to the analyte and indicator until the indicator changes color in reaction to the titrant saturation threshold, reflecting arrival at the endpoint of the titration. Depending on the endpoint desired, single drops or less than a single drop of the titrant can make the difference between a permanent and temporary change in the indicator. When the endpoint of the reaction is reached, the volume of reactant consumed is measured and used to calculate the concentration of analyte by where C a is the concentration of the analyte, typically in molarity; C t is the concentration of the titrant, typically in molarity; V t is the volume of the titrant used, typically in liters; M is the mole ratio of the analyte and reactant from the balanced chemical equation; and V a is the volume of the analyte used, typically in liters. Preparation techniques Typical titrations require titrant and analyte to be in a liquid (solution) form. Though solids are usually dissolved into an aqueous solution, other solvents such as glacial acetic acidor ethanol are

Titration Volumetric analysis is quantitative analysing measuring volumes to find the concentration of a solution. This involves reacting a solution of known concentration with one of unknown concentration to determine the equivalence point. The equivalence point is reached when the reactants have completely reacted together in the ratio of the mole quantities given in the balanced equation for the reaction. The equivalence point for NaOH (aq) + HCl (aq)  NaCl (aq) + H 2 O (l) is when sodium hydroxide and hydrochloric acid have completely reacted in a 1:1 mole ratio. The equivalence point for 2KOH (aq) + H 2 SO 4(aq)  K 2 SO 4(aq) + 2H 2 O (l) is when potassium hydroxide and sulfuric acid have completely reacted in a 1:1 mole ratio. Describe the equivalence point for the reaction: 3KOH (aq) + H 3 PO 4(aq)  K 3 PO 4(aq) + 3H 2 O (l) ____________________________________________________________________________________________ ____________________________________________________________________________________________ The equivalence point for a neutralisation reaction is measured by choosing an acid-base indicator that changes colour about the pH of the salt solution that was formed at the equivalence point. strong acid + strong base  neutral salt solution pH about 7 bromothymol blue or litmus indicator solution change colour about pH 7 strong acid + weak base  acid salt solution pH below 7 methyl orange indicator solution changes colour about pH 4 weak acid + strong base  basic salt solution pH above 7 phenolphthalein indicator solution changes colour about pH 9 The point at which the indicator changes colour is called the end point. An indicator is chosen with end point as close as possible to the equivalence point.

2006

600 Journal of Chemical Education • Vol. 83 No. 4 April 2006 • www.JCE.DivCHED.org Figure 2. Providing some information. Part 2: A Californian, who has more experience with earthquakes, recalls seeing a page in the phone book with information that might be useful to you. He happens to have carried the page because he is going to do some backpacking on the way home and is concerned about running out of potable water. (A copy of that page appears as Figure 3).

Mohr Method, 2018

Objective: Determination of chloride in solid and liquid samples by the Mohr Method Learning Outcome: • Students understand the terms volumetric analysis, morarity, molality normality and redox titration. • Students acquire the skill to prepare standard solutions of silver nitrate and sodium chloride. • Students understand the apparatus used for a titration. • Students acquire the skill to perform the precicpitation-titration in the real lab after understanding the different steps. Titration is a process by which the concentration of an unknown substance in solution is determined by adding measured amounts of a standard solution that reacts with the unknown. Then the concentration of the unknown can be calculated using the stoichiometry of the reaction and the number of moles of standard solution needed to reach the so called end point. Precipitation titrations are based upon reactions that yield ionic compounds of limited solubility. Classification of methods precipitation titration (on titrant): 1.

Chemistry - A European Journal, 2010

Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to a solution. To dilute a solution means to add more solvent without the addition of more solute. A serial dilution is any dilution where the concentration decreases by the same quantity in each successive step. The antibody titer is a test that detects the presence and measures the amount of antibodies within a person's blood. It determination of the concentration of a specific antibody in the patient's serum or to determine the strength of antigen expression on different red cell samples. The amount and diversity of antibodies correlates to the strength of the body's immune response. A titer may be used to prove disease. The immune system produces antibodies to mark invading foreign substances for destruction or to neutralize them before they can cause a disease or problem to body system.