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Chemistry - SCH4U1 > Unit 4 - Chemical Systems and Equilibrium > Flashcards

Unit 4 - Chemical Systems and Equilibrium Flashcards

1
Q

chemical equilibrium

A

the state of a reaction in which all reactants and products have reached constant concentrations in a closed system

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2
Q

dynamic equilibrium

A

a balance between forward and reverse processes that are occurring simultaneously at equal rates

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3
Q

equilibrium position

A

the relative concentrations of reactants and products in a system are in dynamic concentration

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4
Q

reversible reaction

A

a chemical reaction that proceeds in both the forward and reverse directions, setting up an equilibrium in a closed system (⇌)

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5
Q

types of equilibrium

A
  • chemical equilibrium: a dynamic equilibrium between reactants and products in a chemical reaction in a closed system (e.g. N2O4(g) ⇌ 2NO2(g))
  • phase equilibrium: a dynamic equilibrium between different states of a pure substance in a closed system (e.g. H2O(ℓ) ⇌ H2O(g))
  • solubility equilibrium: a dynamic equilibrium between a solute and a solvent in a saturated solution in a closed system (e.g. CuSO4(s) ⇌ Cu+2(aq) + SO4-2(aq))
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6
Q

equilibrium law

A

the mathematical description of a chemical system at equilibrium; applies to gaseous and aqueous chemical equilibria

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7
Q

equilibrium constant (K)

A

a constant numerical value at a given temperature, defining the equilibrium law for a given system

K = [products]p ÷ [reactants]r

if K > 1, then the products are favoured in the reaction and the reaction may go to completion
if K ≐ 1, then the concentration of reactants and products is approximately equal
if K < 1, then virtually no products are formed, and reactants are favoured in the reaction

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8
Q

homogeneous equilibrium

A

a chemical equilibrium system in which all reactants and products are in the same state of matter (i.e. all gases or aqueous)

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9
Q

heterogeneous equilibrium

A

a chemical equilibrium system in which all reactants and products are present in at least two different states

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10
Q

Le Châtelier’s Principle

A

When a chemical system at equilibrium is disturbed by a change in a property, the system adjusts in a way that counteracts the change.

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11
Q

equilibrium shift

A

a change in concentrations of reactants and products in order to restore an equilibrium shift (different from the original equilibrium concentration)

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12
Q

Le Châtelier’s Principle and changes in concentration

A
  • addition of more reactant, or removal of product results in the formation of more product (equilibrium shifts to the right)
  • addition of more product or removal of reactant results in the formation of more reactant (equilibrium shifts to the left)
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13
Q

Le Châtelier’s Principle and changes in energy (temperature)

A
  • if the system is cooled, it will shift in the direction that produces heat (exothermic)
  • if the system is heated, it will shift in the direction that absorbs heat (endothermic)
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14
Q

Le Châtelier’s Principle and changes in gas volume

A
  • when volume decreases (pressure increases), the equilibrium shifts to the side where less moles of gas are produced
  • when volume increases (pressure decreases), the equilibrium shifts to the side where more moles of gas are produced

all concentrations initially increase or decrease with volume, because they are all gases

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15
Q

changing an equilibrium system without affecting equilibrium position

A
  • catalysts: the Ea of both the forward and reverse reactions are lowered by the same amount
  • inert gas (e.g. helium): the total pressure of the system is increase, but the reaction is not pushed in one direction over another
  • state of reactants: equilibrium is not affected by adding a substance in a different state of matter from the state of the substances reacting in the chemical reaction
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16
Q

reaction quotient (Q)

A

the product of the concentrations of the products, divided by the product of the concentrations of the reactants, for a chemical reaction that is not necessarily at equilibrium

K = [products]p ÷ [reactants]r

if Q < K, the chemical system will shift to the right to reach equilibrium (reactants are favoured)
if Q = K, no shift will occur (the chemical system is at equilibrium)
if Q > K, the chemical system will shift to the left to reach equilibrium (products are favoured)

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17
Q

dissociation

A

the separation of ionic compounds into ions

e.g. AgI(s) ⇌ Ag+(aq) + I-(aq)

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18
Q

ionization

A

the separation of covalent compounds into ions

e.g. HCl(aq) → H+(aq) + Cl-(aq) (strong acid)

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19
Q

solubility

A
  • the quantity of solute that dissolves in a given quantity of solvent at a particular temperature
  • the concentration of a saturated solution at a particular temperature
  • often expressed in g/L or g/100mL
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20
Q

solubility product constant (Ksp)

A

the value obtained from the equilbirum law applied to a saturated solution

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21
Q

common ion effect

A

a reduction in the solubility of an ionic compound, due to the presence of a common ion in solution

22
Q

The Arrhenius Theory of Acids and Bases

A

acids produce hydrogen ions when dissolved in water
e.g. HCl(aq) → H+(aq) + Cl-(aq)

bases produce hydroxide ions when dissolved in water
e.g. NaOH(s) → Na+(aq) + OH-(aq)

23
Q

The Brønsted-Lowry Theory of Acids and Bases

A

acids are proton donors
e.g. HF(aq) + H2O(ℓ) → H3O+(aq) + F-(aq)

bases are proton acceptors
e.g. NH3(g) + H2O(ℓ) → NH4+(aq) + OH-(aq)

24
Q

conjugate acid

A

the substance that forms when a base accepts a proton

25
Q

conjugate base

A

the substance that forms when an acid loses a proton

26
Q

conjugate acid-base pair

A

two substances related to each other by the donating and accepting of a proton; formulas differ by only a proton

27
Q

amphiprotic substance

A

a substance that is able to donate or accept a proton, and thus act as a Brønsted-Lowry acid or a Brønsted Lowry base

e.g. HCO3-(aq) + H2O(ℓ) → H2CO3(aq) + OH-(aq) (hydrogen carbonate ion acts as a base)
e.g. HCO3-(aq) + H2O(ℓ) → CO3-2(aq) + H3O+(aq) (hydrogen carbonate ion acts as an acid)

28
Q

strong acid

A

an acid that ionizes almost 100% in water, producing hydrogen ions

e.g. HBr(aq) → H+(aq) + Br-(aq)

29
Q

weak acid

A

an acid that only partially ionizes in water, producing hydronium ions

e.g. HNO2(aq) + H2O(ℓ) ⇌ NO2-(aq) + H3O+(aq)

30
Q

strong base

A

a base that dissociates completely in water, producing hydroxide ions

e.g. KOH(s) → K+(aq) + OH-(aq)

31
Q

weak base

A

a base that only partially reacts with water, producing hydroxide ions

e.g. NH3(g) + H2O(ℓ) ⇌ NH4+(aq) + OH-(aq)

32
Q

monoprotic acid

A

an acid that possesses only one ionizable hydrogen atom

33
Q

polyprotic acid

A
  • an acid that possess more than one ionizable hydrogen atom
  • they can donate or accept more than one proton, but only one proton is transferred per reaction
34
Q

autoionization of water

A

the transfer of a hydrogen ion from one water molecule to another to produce a hydronium ion and a hydroxide ion

H2O(ℓ) + H2O(ℓ) ⇌ H3O+(aq) + OH-(aq)

35
Q

ion-product constant for water (Kw)

A

the equilibrium constant for the autoionization of water

Kw = 1 × 10-14

36
Q

pH

A
  • the negative logarithm of the concentration of hydronium ions in an aqueous solution
  • pH increases by 1 for 10× more [H3O+(aq)]
  • pH = -log[H3O+(aq)]

pH < 7; acid
pH = 7; neutral
pH > 7; basic

37
Q

pOH

A
  • the negative logarithm of the concentration of hydroxide ions in an aqueous solution
  • pH increases by 1 for 10× more OH-(aq)]
  • pOH = -log[OH-(aq)]

pOH > 7; acid
pOH = 7; neutral
pOH < 7; basic

38
Q

pH and pOH formulas

A
  • Kw = [H3O+(aq)][OH-(aq)]
  • pH = -log[H3O+(aq)]
  • pOH = -log[OH-(aq)]
  • pH + pOH = 14
  • [H3O+(aq)] = 10-pH
  • [OH-(aq)] = 10-pOH
39
Q

acid ionization constant (Ka)

A

Ka = [H3O+(aq)][A-(aq)] ÷ [HA(aq)]

40
Q

base ionization constant (Kb)

A

Ka = [BH+(aq)][OH-(aq)] ÷ [B(aq)]

41
Q

the relationship between Kw, Ka, and Kb

A

KaKb = Kw

42
Q

neutral solution formed by salt

A
  • strong acid + strong base
  • dissociated ions are too weak to react with water, and do not form an equilibrium with water
  • [H3O+(aq)] = [OH-(aq)]

e.g. LiCl(aq) → Li+(aq) + Cl-(aq)

43
Q

basic solution formed by salt

A
  • weak acid + strong base
  • negatively charged ion reacts with water and develops an equilibrium
  • [H3O+(aq)] < [OH-(aq)]

e.g. KF(aq) → K+(aq) + F-(aq)

F-(aq) + H2O(ℓ) → HF(aq) + OH-(aq)

44
Q

acidic solution formed by salt

A
  • strong acid + weak base
  • positively charged ion reacts with water and develops an equilibrium
  • [H3O+(aq)] > [OH-(aq)]

e.g. NH4Cl(aq) → NH4+(aq) + Cl-(aq)

NH4+(aq)</sub> + H2O(ℓ) → NH3(aq) + H3O+(aq)

45
Q

titration

A
  • the addition of precise volumes of a solution in a burette to a measured volume of a sample solution
  • often used to determine the concentration of a substance in the sample
46
Q

sample

A

the solution being analyzed in a titration

47
Q

titrant

A

the solution in a burette during a titration

48
Q

burette

A

a calibrated tube used to deliver variable-known volumes of a liquid during a titration

49
Q

equivalence point

A
  • the point in titration when neutralization is complete
  • the two solutions are stoichiometrically equal
  • neither reactant is in excess
50
Q

endpoint

A

occurs just as the indicator changes colour

51
Q

pH curve

A

a graph of pH plotted against volume of titrant added in an acid-base titration (titration curve)

Chemistry - SCH4U1 (5 decks)

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