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A IB Chemistry SL > 8,9 - Acids & Base, Redox > Flashcards

8,9 - Acids & Base, Redox Flashcards

1
Q

oxidation number of elements (eg.O2, Cl2, N2)

A

0

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2
Q

oxidation number of ions (eg.Zn2+, Cl-)

A

same as their charge

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3
Q

G1 metals have oxidation state of

A

+1

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4
Q

G2 metals have oxidation state of

A

+2

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5
Q

O has oxidation state of

A

-2

except in peroxides (e.g. H2O2), where it is −1

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6
Q

H has oxidation state of

A

+1

except in certain metal hydrides (e.g. NaH), where it is −1

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7
Q

F and Cl have oxidation state of

A

-1

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8
Q

the sum of oxidation number in a compound is

A

0

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9
Q

in a compound/ion, the negative oxidation number is always given to

A

the more electronegative element

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10
Q

oxidizing agent

A

gets reduced (gains electrons)
= ox.no. decrease

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11
Q

reducing agent

A

gets oxidized (lose electrons)
= ox.no. increases

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12
Q

transition metals are characterized by

A

having variable oxidation states

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13
Q

more reactive metals act as

A

reducing agents (get oxidized, lose electrons to less reactive metal ions)

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14
Q

more reactive metals can do what to less reactive metals?

A

displace less reactive metals from their compounds (more reactive metals like to be in ion form!)

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15
Q

In redox titrations, an ____ is titrated against a ____

A

oxidizing agent
is titrated against
reducing agent

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16
Q

How is endpoint indicated in the Manganate(VII) Titrations?

A

purple color disappears

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17
Q

How is endpoint indicated in the **Iodine-Thiosulfate ** Titrations?

A
  1. light brown of the iodine turns paler as it is converted to colorless iodide ions
  2. add starch to clarify endpoint → blue/black
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18
Q

The Winkler Method is used to measure

A

concentration of dissolved oxygen in freshwater systems

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19
Q

Voltaic cells: what materials should the external connection and salt bridge be made of? why?

A
  • external: metallic wire; to allow electron to flow
  • salt bridge: aqueous electrolyte; to allow ions to flow
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20
Q

Electrolysis happens when

A

flow of current causes ionic compound to split up and form new substances

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21
Q

applications of electrolysis

A
  • purifying copper
  • plating metals with silver/gold
  • extracting reactive metals (eg. Al)
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22
Q

electrolyte is

A

the substance passed by current and splits up

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23
Q

What happens to ions during electrolysis?

A
  • -ions move to the anode → lose e-
  • +ions move to the cathode → gain e-
  • Electrically neutral molecules are released
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24
Q

how is current conducted in an electrolytic cell?

A
  • e- move by external circuit
  • ions move through the electrolyte
25
Q

oxidation always occurs at the

A

anode

26
Q

reduction always occurs at the

A

cathode

27
Q

Brønsted-Lowry acid

A

proton donor

28
Q

Brønsted-Lowry base

A

proton accepter

29
Q

conjugate acid-base pair

A

two species different by a H+ ion
eg. H2O and H3O+

30
Q

a strong acid always has a

A

weak conjugate base

31
Q

amphiprotic vs amphoteric

A

amphiprotic: can act both as proton donors and acceptors

amphoteric: can act as both acid and base

all amphiprotic are amphoteric, but not all amphoteric are amphiprotic (eg. Al2O3)

32
Q

acid + metal →

A

salt + H

33
Q

acid + metal oxide →

A

salt + H2O

34
Q

acid + metal hydroxide →

A

salt + H2O

35
Q

acid + metal carbonate →

A

salt + water + CO2

36
Q

acid + base →

A

salt + water

37
Q

How can you compare the strength of acids?

A
  1. pH value
  2. Reactivity: put the same metal into same concentration of different acid solutions - stronger acids have a higher H+ concentration thus will react more vigorously with metals than weak acids. This can be seen as: more effervescence, more exothermic, metal dissolves faster…
  3. Electrical conductivity: stronger acid has a higher H+ concentration → conducts electricity better
38
Q

describe the color of litmus indicator

A

acid = pink
base = blue

39
Q

describe the color of methyl orange indicator

A

acid = red
base = yellow

40
Q

describe the color of phenophthalein indicator

A

acid = colorless
base = pink

41
Q

pH

A

measures the concentration of H+ ions

pH = -log [H+]

42
Q

10.0 cm3 of nitric acid solution of pH = 1.0 is mixed with 990.0 cm3 of distilled water. What is the pH of the final solution?

A

volume increase by a factor of 10^2 (from 10 to 1000) → concentration decrease by a factor of 10^2 → pH increase by 2 units

43
Q

a change by 1 pH unit =

A

a change by 10-fold in H+

44
Q

Kw =

A

[H+] [OH-]

45
Q

Determine the pH of a solution made by dissolving 5.00 g of KOH in 250 cm3 of distilled water.

A
  1. [KOH] = [OH-] = (5/56.1)/0.25 = 0.357 mol/dm3
  2. [H+] = Kw/[OH-] = 1x10-14/0.357 = 2.8x10-14
  3. pH = -log[H+] = 13.55
46
Q

strong acid

A

completely dissociates in aqueous solutions; irreversible reaction as the equilibrium position is far over to the right

47
Q

weak acid

A

partially dissociates in aqueous solutions; reversible reaction as the equilibrium position more over to the left

48
Q

examples of strong acid

A

基本常见的都是: HCl, HNO3, H2SO4

49
Q

examples of weak acid

A

most organic acids, HCN, H2S,H2CO3

50
Q

examples of strong base

A

G1 metal hydroxides

51
Q

examples of weak base

A

NH3, amines, some transition metal hydroxides

52
Q

HCl → H+ + Cl- can also be written as

A

HCl + H2O → H3O+ + Cl-

53
Q

acid rain

A

rain with a pH below 5.6

54
Q

Rain is naturally acidic because

A

dissolved CO2 in the atmosphere form carbonic acid

H2O (l) + CO2 (g) ⇌ H2CO3 (aq)

55
Q

acid deposition - sulfur

A

from burning fossil fuel…
1. S + O2 → SO2
2. SO2 + O2 → SO3
3. SO2 + H2O → H2SO3
SO3 + H2O → H2SO4

56
Q

acid deposition - nitrogen

A

from internal combustion engine…
1. N2 + O2 → NO
2. NO + O2 → NO2
3. NO2 + H2O → HNO2 + HNO3

57
Q

effects of acid rain

A
  • corrosion of limestone buildings:
    CaCO3 + H2SO4 → CaSO4 + CO2 + H2O
    CaCO3 + 2HNO3 → Ca(NO3)2 + CO2 + H2O
  • important ions leach from soil → plants die, eutrophication (excessive algal growth that results in oxygen depletion)
58
Q

methods to reduce SO2 emission

A

pre-combustion:
* use renewable energy sources or fuel with less sulfur content
* sulfur is removed by reacting with hydrogen (hydrodesulfurization) → make H2SO4

post-combustion:
* pass waste gases through a wet slurry of CaO and CaCO3, which react with the SO2 and produce CaSO4 → make plaster

A IB Chemistry SL (9 decks)

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