# بسم الله الرحمن الرحيم.  To determine the concentration of a given acid by its titration against alkali.

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بسم الله الرحمن الرحيم

 To determine the concentration of a given acid by its titration against alkali.

 An acid is a substance that increases the concentration of H 3 O + (hydronium ion) in aqueous solution.  A base: is a substance that decreases the concentration of H 3 O + in aqueous solution.  A decrease in [H 3 O + ] requires an increase in [OH - ], so we can define the base as a substance that increase the concentration of OH - in aqueous solution.  H + is called a proton, because a proton is all that remains when a hydrogen atom loses its electron.  Hydronium ion (H 3 O + ) is a combination of H + with H 2 O.

Bronsted and Lowry definition of acids and bases An acid is a proton donor A base is a proton acceptor. Example HCl is an acid because it donates a proton to H 2 O to form H 3 O + HCl (l) + H 2 O H 3 O + (aq) + Cl - (aq) Salts: - Any ionic solid such as ammonium chloride is called salt. It can be thought of as the product of an acid base reaction. - Most salts are strong electrolytes, i.e. they dissociate almost completely into their component ions when dissolved in water NH 4 + Cl -  NH 4 + + Cl -

 A standard solution (standard titrant) is a reagent of known concentration that is used to carry out a titrimetric analysis  Titration: is a procedure performed by adding a standard solution from a buret or other liquid-dispensing devices to a solution of the analyte until the reaction between the two is judged complete.  Equivalence point in titration is reached when the amount of added titrant is chemically equivalent to the amount of analyte in the sample  E.g. AgNO 3 + Cl -  AgCl mol mol  (Equivalent points can ’ t be determined experimentally)  End point is the point in a titration when physical change occurs that is associated with the condition of chemical equivalence.  Indicator: a chemical compound that change it ’ s color or other physical property at or near the equivalence point.

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