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EA PREP > chemistry U3 T1 > Flashcards

chemistry U3 T1 Flashcards

1
Q

definition dynamic equilibrium?

A

balance is maintained and reaction is continuously happening. Reactants and products are being created/used up continuously at the same rate so forwards and reverse reactions are equal.

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2
Q

definition; open system

A

reaction vessel with no lid so matter and energy can escape

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3
Q

definition closed system

A

reaction vessel has a lid so matter can escape but not energy

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4
Q

what does increasing volume do

A

decrease pressure, decrease concentration thus equilibrium moves to side w/ more moles

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5
Q

what does decreasing volume do

A

increase pressure, increase concentration thus equilibrium moves to side w/ less moles

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6
Q

definition; le chatliers principle

A

if an equilibrium system is subject to change the system will adjust proportionally to oppose the change

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7
Q

what causes a disturbance

A

volume
pressure (only gas form)
temperature
adding or removing substances
diluting aqueous solution

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8
Q

definition; temperature

A

measure of average kinetic energy in a system

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9
Q

for endo and exo, which is a positive H (enthalpy change)? What side is heat on?

A

endo positive (left), exo negative (right)

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10
Q

endo vs exo?

A

endo absorbs heat and cools surroundings
exo releases heat and heats surroundings

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11
Q

3 things that dont change equilibrium position?

A
  1. Catalyst as it lowers activation energy and speeds up reactions however it doesnt change equilibrium position.
  2. Changing temperature with H=0 (0 enthalpy) as its neither endo or exo.
  3. Changing pressure w/ equal moles on either side.
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12
Q

what is Kc? What does <1> mean?

A

Its the ratio of reactants to products when reaction is at equilibrium.
Less than 1 is reactants favoured
More than 1 is products favoured

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13
Q

What is Kc for a reverse reaction (formula)?

A

Kc (reverse)= 1/Kc (forwards)

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14
Q

What can change Kc?

A

temperature

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15
Q

definition; proton donor

A

Substance that can donate H^+ (hydrogen ion)

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16
Q

definition; monoprotic acid

A

acid that can donate 1 H+ (hydrogen ion) per molecule

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17
Q

definition; polyprotic acid

A

acid that can donate 2+ H+ (hydrogen ion) per molecule

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18
Q

Acid vs base?

A

acid donates protons
base accepts protons

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19
Q

Strong vs weak acids/bases?

A

strong completely dissociate (ionisation) (releasing all H+)
weak partially dissociate (releasing some H+)

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20
Q

concentrate vs dilute acids/bases?

A

concentrate has high concentration/molarity and large amounts are dissolved in a solution
dilute has low concentration/molarity and small amounts are dissolved in a solution

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21
Q

Whats an electrolyte?

A

substance that conducts electricity when melted or dissolved in a solution. Conductivity in a solution depends entirely on the presence of charged particles.

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22
Q

what solutions conduct electricity best to worst? Why?

A

the one with most hydrogen ions conducts the best. so;
Concentrated strong acid > concentrated weak/dilute strong > dilute weak

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23
Q

What is water’s self-ionisation reaction (unlikely)? What regularly occurs?

A

2 H2O <-> H3O+ + OH-

H2O <-> H+ + OH-

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24
Q

What is Kw?

A

the equilibrium constant of self-ionisation of water.

25
Definiton; Qc? What does it mean when comparing Qc to Kc?
is the reaction quotient, measure of the relative amounts of products and reactants present in a reaction at a given time (calculated the same way as Kc). if Qc is bigger than Kc - too many products if Qc is smaller than Kc - too many reactants
26
Definition; pH?
is a measure of hydrogen ion concentration in a solution and therefore a measure of acidity or alkalinity of a solution
27
Definition; pOH?
is a measure of hydroxide ion concentration in a solution and therefore a measure of the basicity of a solution
28
What equals 14?
pOH + pH
29
What is a conjugate acid and base?
Conjugate acid is an acid formed after a base accept an H+ (originally a base, then accepts proton (H+), now conj base) Conjugate base is a base formed when an acid loses an H+ (originally acid, then donated a proton, now conj base)
30
Identify the conjugate pair?
HA + B <-> A- + HB+ Acid + base <-> conj. base + conj acid so acid and conj base/HA and A- = pair base and conj acid/ B and HB+ = pair
31
Definition; Amphiprotic? 2 Examples?
is a molecule or ion that can either donate or accept a proton so can act as acid or base. e.g. HCO3^- and H2O
32
Conjugate Acid and base strengths?
Strong acid -> very weak base weak acid <-> weak base Strong base -> very weak acid
33
What pair type forms equilibrium reactions?
weak acid <-> weak base
34
Strongs acids (3)
H2SO4 - sulphuric HCl - hyrochloric HNO3 - nitric
35
Strong Bases (2)
Any group 1 + Hydroxide Barium + hydroxide
36
Weak acids (3)
H2CO3 - carbonic HCO3 - hydrogen carbonate ion R COOH
37
Weak bases (3)
NH3 - ammonia R NH2 R NH R
38
Definition; buffer solutions?
is a solution that resists changes in pH when small quantities of acids or bases are added. It contains appreciable amounts of 1 - weak acids and its conjugate base, 2 - weak base and its conjugate acid
39
Example of a mixture of weak acid with salt of its conjugate base
acetic acid/ sodium acetate
40
Example of a mixture of weak base with salt of its conjugate acid
ammonia/ ammonium chloride
41
How do buffers work? (2)
1. when a strong base is added, the acid present in the buffer neutralise the OH- 2. When a strong acid is added, the base present in the buffer neutralise the H3O+
42
Definition; Ka?
equilibrium constant for the dissociation of an acid in an aqueous solution
43
Definition; Kb?
equilibrium constant for the dissociation of a base in an aqueous solution
44
What do lower and higher levels of Ka and Kb mean?
High Ka/b means more products and more dissociation Lower Ka/b means less products and less dissociation
45
If using a weak acid indicator e.g. HA (blue) + H2O <-> A- (red) + H3O+ in acidic and then basic conditions, what would happen?
Acidic conditions; [H3O+] increases, pushes equilibrium left creating more [HA], and colour would be blue. Basic conditions; [H3O+] decreases, pushes equilibrium right creating more [A-], and colour would be red.
46
If using a weak base indicator e.g. B (blue) + H2O <-> BH+ (red) + OH- in acidic and then basic conditions, what would happen?
Acidic conditions; [OH-] decreases, pushes equilibrium right creating more [BH+], and colour would be red. Basic conditions; [OH-] increases, pushes equilibrium left creating more [B], and colour would be blue.
47
What is equivalence point?
the point in a titration when the reactants have reacted in the molar ratio of the balanced chemical equation.
48
Ka/b and PKa/b of stronger acids/bases vs weak acids/bases
Strong: have higher Ka/b values and lower PKa/b values Weak: have lower Ka/b values and higher PKa/b values
49
Neutralisation reactions?
acid + base -> salt + water
50
Analyte vs titrant?
Analyte is an unknown concentration of solution (often in flask) Titrant is a known concentration (often in burette)
51
Stoic formula?
n=cv
52
What is the buffer region?
pH=pKa in weak acid and pOH=pKb in weak base
53
Provide an example of a physical and chemical change?
melting ice harber process forming NH3, acid dissociation
54
As heat energy is applied to a solid, what occurs to its kinetic energy and the changes that take it from s to l to g?
As heat increases so does kinetic energy. Particles vibrate out of the orderly structure of a solid and start moving with the containing (l form). If enough energy is supplied to counteract intermolecular forces and ionic bonds, particles are separated and form gases.
55
P71 Q6, P72 Q20a, P48 Q3&4
56
If increasing temperature increased Kc from 0.32 to 0.88, was the reaction endo or exo?
endo
57
If you have N2 + O2 -> 2NO and it was at equilibrium what would happen?
2 moles of gas on left and right so the increased volume would increase concentration but position of equilibrium would not change
58
P72 Q16, P71 Q7

EA PREP (9 decks)

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