Review cation Ion charges anion Ionic compounds are made of cations and anions. The cation is always first followed by the anion. Ionic compounds are NEUTRAL, so you may have to criss cross the charges of your ions. Ex: Mg2+ Cl- MgCl2

Neutralization

Neutralization Reactions A neutralization reaction is a reaction in which an acid and a base react to produce a salt and water Acid + Base  Salt + H2O A salt is an ionic compound made up of a cation and an anion

Example: NaCl + H2O salt water HCl + NaOH  Mg(OH)2(aq) + 2HCl(aq)  acid base Mg(OH)2(aq) + 2HCl(aq)  HNO3 + NaOH  Ba(OH)2 + HCl  H2SO4 + CsOH  HNO3 + KOH 

Practice Problem #1 C NH3 + HCl  NH4+ + Cl- base acid

Reading a Buret

Titrations

Titration Purpose - To find the unknown concentration of a solution. Procedure – Add a known amount of solution of known concentration to a solution of unknown concentration.

Buret – A piece of glassware used for dispensing accurate volumes of a solution. The solution of known concentration is in the buret.

Analyte/Unknown Solution - The solution that is being analyzed Analyte/Unknown Solution - The solution that is being analyzed. It is the solution of unknown concentration Titrant/Standard Solution - The solution of known concentration that is added to the analyte

Titrant or Standard Solution (known concentration) stopcock Analyte (unknown concentration)

Equivalence Point - when the acid and base are mixed and the number of hydrogen ions equal the number of hydroxide ions. [H+] = [OH-]

Acid–base indicator – A chemical dye whose colors are affected by acidic and basic solutions. A common acid base indicator for titration is phenolphthalein. End point is the point which the indicator used in titration changes color.

Equivalence Point vs. End Point The equivalence point is when [H+] = [OH-]. You cannot see this. The end point is when you see a change in color in the indicator. The equivalence point should be very close to the end point. To make sure this happens, an appropriate indicator needs to be chosen.

Titration Youtube Explanation of titration Titration using pheonthalein

At the Endpoint Past the endpoint (overshot) Before the endpoint

Calculations: Example 1 HC2H3O2 + NaOH  H2O + NaC2H3O2 In a titration, the volume of base needed was 9.50mL of 0.500 M NaOH to reach equivalence point. The volume of HC2H3O2 acid titrated was 5.89 mL. Find the molarity of the acid.

HC2H3O2 + NaOH  H2O + NaC2H3O2

Example 2 If you are doing a neutralization where there is more than one hydrogen on the acid, your mole ratio will not be one to one. Example: H2SO4 + 2RbOH  2H2O + Rb2SO4