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Chem 26.1 Midterms Review
Prepared by: CMFR
Expt 1: Statistical Concepts • Significant Figures • Accuracy vs. Precision • Mean, Median • Average deviation, variance, standard deviation, relative standard deviation, coefficient of variation, pooled standard deviation, range and relative range • Absolute and relative error • Confidence Limits • Q-Test
Expt 1: Statistical Concepts • Use of analytical balance • Weighing techniques • Types of errors: – Systematic (determinate) – Random (indeterminate) – Gross
Expt 2: Solution Preparation • Ways of expressing concentration • Aliquot factor vs. Dilution factor
Expt 3: Kinetics of Thiosulfate and HCl
• Method of Initial Rates – Ratio and proportion
• Effect of temperature on reaction rate: Arrhenius equation k=Ae-Ea/RT • Rate law for reaction of thiosulfate with HCl: rate = k[S2O32-] • Reaction mechanisms: only the ratedetermining steps appear in the rate law – Thus the correct mechanism is multi-step process b or 4 (see your lab manual)
Expt 4: Common Ion Effect and Buffers • Le Chatelier’s Principle! • Common ion effect – consequence of Le Chatelier’s principle – Salt is less soluble in solution containing an ion which is the same as one of the constituent ions of that salt
• Buffer solution – Resists large changes in pH
Expt 4: Common Ion Effect and Buffers
Different approaches to calculating pH: • ICE table • Henderson Hasselbalch equation
Color changes brought about by the indicator also signify changes in pH.
Expt 5: Shifting Equilibrium • Q = Keq equilibrium • Q > Keq (right to left/backward) • Q < Keq (left to right, more products) • Properties of Keq when adding/subtracting equations – Adding equations: Keq’s are multiplied – Subtracting: Keq’s are divided – Multiplying by a coefficient: raise Keq to the nth power where n = coefficient multiplied to equation
• Different types of Keq’s – Ka, Kb, Ksp, Kf , etc…
Expt 5: Shifting Equilibrium • Reactions in Test tubes 1-6