Equilibrium -physical Flashcards

1
Q

Equilibrium definition

A

A chemical reaction where reactant and products concentrations remain constant

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2
Q

Rate equation for equilibrium

A

K= [C]^c [D]d/[A]a [B]b

Where a,b,c,d

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3
Q

If the equilibrium position lies to the left

A

Products < reactants
K<1
More reactants than products

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4
Q

If the equilibrium position lies to the right

A

Products >reactants
K>1

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5
Q

Equilibrium constant rules

A

Not affected by concentration and pressure
When temperature increases the value of K increases for the endothermic reaction
When temperature decreases the value for K increases for the exothermic reaction

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6
Q

Endothermic enthalpy change

A

Positive

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7
Q

Exothermic enthalpy change

A

Negative

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8
Q

Water equilibrium

A

H2O +H2O —> H3O+ +OH-

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9
Q

Kw formula

A

Kw = [H3O+] [OH-]
=1.01x10^-14

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10
Q

Kw rules

A

Affected by temperature

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11
Q

pH formula

A

pH = -log[H+]

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12
Q

H+ concentration formula

A

10^-pH

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13
Q

Concentration calculation and pH calculation tips

A

Always write out the dissociation equation

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14
Q

Strong acids

A

Acids that completely dissociate into ions in aqueous solution

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15
Q

Strong bases

A

Bases that completely dissociate into ions

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16
Q

Weak acids

A

Acids which partially dissociate into ions in aqueous solution

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17
Q

Weak bases

A

Bases which partially dissociate into ions in aqueous solution

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18
Q

Strong acids examples

A

Hydrochloric, nitric and sulphuric.

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19
Q

Weak acids examples

A

Ethanoic, sulphurous and carbonic

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20
Q

Strong bases examples

A

Metal hydroxides and oxides

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21
Q

Weak bases examples

A

Ammonia and amines

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22
Q

Brønsted-Lowry acids definition

A

A proton donator since H+ ions are protons

23
Q

Brønsted-Lowry bases definition

A

A proton acceptor since H+ ions are protons

24
Q

Conjugate acid

A

The proton donator in the reverse reaction

25
Q

Conjugate base

A

The proton acceptor in the reverse reaction

26
Q

Amphoteric

A

Where a substance can act as an acid and base

27
Q

Weak acids properties

A

Higher pH
Lower conductivity
Slower rate of reaction

28
Q

Strong acids properties

A

Lower pH
Higher conductivity
Faster rate of reaction

29
Q

Strong bases properties

A

Higher pH
Higher conductivity
Faster rate of reaction

30
Q

Weak acids properties

A

Lower pH
Lower conductivity
Slower rate of reaction

31
Q

Rules for neutralising strong and weak acids and bases

A

The quantities of acid and bases used in a reaction are based on the balanced equation, not in acid strength.

32
Q

Ka formula

A

[Products] / [reactants]

32
Q

Unique rule for Ka

A

Don’t put water into the equation

33
Q

pKa formula

A

-logKa

33
Q

PKa scale

A

The lower the pKa the stronger the acid

33
Q

Why is PKa better than pH

A

It isn’t affected by the dilution of water since all species are diluted by the same factor

34
Q

Ka scale

A

The higher the Ka the stronger the acid

35
Q

Weak acid and strong base salt pH

A

More than 7

36
Q

Strong acid and weak base salt pH

A

Less than 7

37
Q

Strong acid and base salt pH

A

7

38
Q

Explanation of strong base and weak acid salt pH

A

The the conjugate base ions will react with hydronium ions supplied by water equilibrium, the water equilibrium will shift to replace the hydronium ions producing an excess of hydroxide ions.

39
Q

Weak base and strong acid salt pH explanation

A

The conjugate acid ions will react with the hydroxide ions supplied by the water equilibrium, the water equilibrium will shift to replace the hydroxide ions producing an excess of hydronium ions.

40
Q

pH of weak acids formula

A

pH = 1/2pKa - 1/2logc

41
Q

Buffer solutions def

A

A solution where the pH remains constant on addition of small amounts of acid or base

42
Q

Acid buffer composition

A

A weak acid
The salt of a weak acid and strong base

42
Q

pH of buffer solution

A

pH = pKa - log[acid]/[salt]

42
Q

Indicator dissociation

A

HIn + H2O —> H30+ + OH-

43
Q

Dissociation constant of indications (Kin)

A

[H3O+] [In-]/[HIn]

44
Q

Titration graph rules

A

pH changes quickly around the endpoint of reaction
The endpoint is the middle of the vertical line.

45
Q

Weak acid strong base indicator

A

Change colour between 7 and 11

46
Q

Strong acid weak base indicator

A

Change colour between 3 and 7

47
Q

Colour change of indicator

A

When H+ concentration is equal to Kin

48
Q

Colour change pH range explanation

A

The colour change is distinguishable when [Hin] and [in-] are within factor of ten therefore pH =Kin +/-1