GAMSAT Physical Chemistry: Acid and Bases – Flashcards
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Arrhenius Definitions
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A: releases H+ B: releases OH-
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Bronsted - Lowry Definitions
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A: Proton donator B: Proton acceptor
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Lewis Definitions
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A: e- pair acceptor B: e- pair donator amphoteric; a molecule that can be both and acid and a base
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Acid ionization constant
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K(a) = [h3o+][A-]/[HA]
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Base ionization constant
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k(b)= [HB+][OH_]/[B]
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pH
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-log10[h3o-]
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pOH
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-log10[OH-]
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pKa
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-log10Ka
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pKb
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-log10Kb
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Strong acids (Name 6)
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HClO4 HI HBr HCl H2SO4 HNO3
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Strong bases (Name 3 Categories with examples)
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Hydroxides: NaOH KOH Ca(OH)2 Sr(OH)2 Amides: KNH2 Ca(NH2)2 Oxides: Na2o CaO BaO
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True or False Oxides develop OH- ions in water making them basic
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True
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Example of a weak acid
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Benzoic
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Example of a weak base
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Ammonia
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Concordant
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Data that is close is value
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Aliquot
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taken with a pipette, proportion of solution used
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Primary standard
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known purity known formula water soluble neither deliquescent nor hydroscopic does not react with O2 in air high molecular mass
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Secondary Standard
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Solution with concentration determined by primary standard
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Titrant
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liquid in burette
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Titre
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amount of titrant used
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Analyte
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liquid being analyzed, liquid in conical flask
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End Point
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Color change of indicator
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equivalence point
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aka stoichiometric point, complete reaction
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color change
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must be for 10 or more seconds
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Indicators: strong acid - strong base
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Phenolphthalein Methyl Orange Bromthymol Blue Phenol Red
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Indicators: Strong acid - weak base
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Methyl Orange
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Equivalence point: Strong acid weak base
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Mid acidic
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Indicators: Strong base - weak acid
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Phenolphthalein
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Equivalence point: Weak Acid - Strong Base
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Low Basic
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Buffer
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resists change in pH
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Acid buffer
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weak acid sharing a common ion with the conjugate base
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Base buffer
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weak base with a common ion with the conjugate acid
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Buffered acid solution is ---- acidic than the weak acid solution alone
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less
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pH of a buffered solution
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pH = pKa +log10([CB]/A) Concentrations at equilibrium
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pOH of a buffered solution
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pOH = pKb + log10([CA]/B) Concentrations at equilibrium
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Buffers are most effective when ...
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[CB] = [A]
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Henderson - Hasselbalch
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approximates pH, pOH of a buffer solution at equilibrium pH = pKa + log10(mol of initial base/ mol of initial acid) pOH = pKlog10(mol of initial acid/mol of initial base)
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Acid buffer solution is best for
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weak acid strong base
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Base buffer solution is best for
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strong acid weak base
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Give three examples of Acid buffers
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CH3COOH and CH3COO- HNO2 and NO2- HClO3 and ClO2 -
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Give two examples of Base Buffers
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NH3 and NH4+ H2PO4- and HPO4^(-2)
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What is the range for pKa for a buffer?
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The pKa of the buffer should be within +/- 1 pKa of the acid given that all other things are equal
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Maximum and minimum acid:base ratio
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Maximum 10:1 Minimum 1:10
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If 50% of a conjugate species then pH = ?
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pKa
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Weak acid
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<10% ionized
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Weak base
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<10% ionized
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Do equal molarities of two substances (one a weak acid and the other a strong acid) have the same pH?
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No
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Polyprotic acids
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Bronsted - Lowry acids that can donate more than 1 proton
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Do polyprotic acids have a single Ka value?
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No they have multiple Ka values the "first" acid has the highest Ka value
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Polyprotic bases
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Bronsted - Lowry bases that can except more than one proton
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Zwitterions
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+ve on one atom and -ve on another, in all phases, e.g. amino acids
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Buffer Capacity
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H30+ / OH- required to change the pH of a solution by 1, past this the buffer loses its ablity to resist change
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If you increase the electronegativity of the atom attached to the H the acidity ---------
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increases
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If halogens are inducted onto a C chain this --------- the acidity of the C chain
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increases
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Inducting and alkyl group onto a C chain leads to and --creased reactivity and an --creased acidity of the C chain
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in de
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Stability of an anion as a result of resonance --------- the acidity o the associated acid.
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enhances
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Arrange the following in order if acidity strength: (Most acidic to least) Phenol Alcohol Carboxylic
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Carboxylic Phenol Alcohol
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Which two effects explain the differences between the acidities of amines, amides and ammonia
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Inductive and Resonance
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Is induction or resonance present in ammonia?
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Neither induction nor resonance are present in ammonia
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Amides have (Equal / Unequal) Resonance forms
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Unequal
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Amine has a e- donating alkyl group making it a weak ---- by which process
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acid by induction
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Alpha carbon
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carbon next to the functional group
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Alpha hydrogen
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Hydrogen attached to the alpha carbon
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In aldehydes and ketones the alpha hydrogen is easily dislodged, what effect does this have in terms of pH
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The easily dislodged alpha hydrogen gives aldehydes and ketones and acidic tendency. The carbon is stabilized by resonance.
