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HSC Chemistry > module six - revision deck > Flashcards

module six - revision deck Flashcards

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1
Q

hydrochloric acid

A

HCl - strong

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2
Q

Hydrofluoric Acid

A

HF - weak

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3
Q

Sulfuric Acid

A

H2SO4 - strong

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4
Q

Nitrous Acid

A

HNO2 - weak

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5
Q

Nitric Acid

A

HNO3 - strong

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6
Q

phosphoric acid

A

H3PO4 - weak

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7
Q

carbonic acid

A

H2CO3 - weak

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8
Q

Sodium Hydroxide

A

NaOH - strong

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9
Q

Calcium Hydroxide

A

Ca(OH)2 - strong

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10
Q

Barium Hydroxide

A

Ba(OH)2 - strong

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11
Q

Sodium Carbonate

A

Na2CO3 - weak

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12
Q

Sodium Bicarbonate

A

NaHCO3 - weak

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13
Q

ammonia

A

NH3 - weak

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14
Q

litmus

A

red below pH 5

blue above pH 7.6

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15
Q

Methyl Orange

A

Red below pH 3.1

Yellow above pH 4.4

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16
Q

bromothymol blue

A

yellow below pH 6

blue above pH 7.6

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17
Q

phenolphthalein

A

colourless below pH 8.3

pink above pH 10.0

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18
Q

acid/base reaction

A

acid + base –> salt + water

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19
Q

acid/carbonate reaction

A

acid + carbonate –> salt + water + carbon dioxide

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20
Q

acid/metal reaction

A

dilute acid + active metal –> salt + hydrogen gas

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21
Q

applications of neutralisation - household

A

antacids - contain bases e.g. mg(OH)2 to neutralise excess HCl in the stomach

toothpaste - alkaline to neutralise the acid in the mouth and to remove food particles that produce acid when they decay

formic acid from bee or ant stings is neutralised by using creams containing bases

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22
Q

applications of neutralisation - industry

A

slaked lime (calcium hydroxide) or limestone (calcium carbonate) is added to neutralise acid in soil for agriculture

gypsum (calcium sulfate) can be used to neutralise alkaline soil

wastewater from industrial processes is acidic or alkaline so needs to be neutralised before entering waterways

23
Q

lavoisier model of acids

A

1780 - Antoine Lavoiser
defined acids as substances containing oxygen
e.g. H2SO4
not all acids contain oxygen (HCl)

24
Q

Davy model of acids and bases

A 
Humphry Davy (1815) 
concluded that acids contain hydrogen
didn't explain why some compounds that contain hydrogen don't behave like an acid
25
Q

Arrhenius model

A 
Svante Arrhenius (1884)
suggested acids were substances that produced hydrogen ions in aqueous solutions, and that bases produced OH ions in aqueous solutions

doesn’t explain why substances that don’t contain hydroxide act like bases (NH3)
limited to reactions in aqueous solution, so doesn’t explain acid-base reactions in other states

26
Q

Bronsted-Lowry Model

A

1923
proposed that an acid-base reaction involved protons being transferred between reaction components and states that acids are proton donors and bases are proton acceptors

does not explain the acidity of acid oxides (SO2 and SO3) and their reactions with basic oxides (CaO)

27
Q

concentration definition

A

the amount of solute in a specified amount of solution

28
Q

strength

A

the degree to which an acid ionises or a base dissociates

  • strong acids are acids in which almost all of the acid molecules ionise to produce a hydrogen ion
29
Q

conjugate acid/base pairs

A

members of a conjugate acid-base pair differ from each other by the presence or absence of the transferrable H
the conjugate base of an acid has one less proton
the conjugate acid of a base has one more proton

30
Q

amphiprotic

A

a substance that can donate or accept a proton

e.g. HSO4, H2O, H2PO4

31
Q

equivalence point

A

the point in a titration where the amount of titrant added is enough to completely neutralise the analyte solution

32
Q

end point

A

the physical sign that the equivalence point has been reached
i.e. when the indicator changes colour

33
Q

titrant

A

substance you want to determine the concentration of

34
Q

aliquot

A

volume measured by the pipette

35
Q

titre

A

volume delivered by the burette

36
Q

primary standard

A

a chemical that can be made up into a solution of accurately known concentration

37
Q

properties of primary standards

A
  • available in highly pure form
  • large molar mass
  • stable in air
  • does not absorb moisture or CO2 from the air
  • readily soluble in distilled water
  • reacts readily with solution of known concentration
38
Q

when back titrations are needed

A
  • it is difficult to determine a definite end point because the reaction occurs too slowly
  • the sample is not soluble in water, but will react with another acid
  • the sample is toxic
  • the sample is volatile
  • the sample is gaseous and in a mixture of gases
  • the sample is fairly unreactive
39
Q

Ka

A

for HA + H2O(l) H3O+ + A-

Ka = [H3O+][A-]/[HA-]

40
Q

Ka of weak vs strong acids

A

Ka of weak acids is very small

Ka of strong acids is very large

41
Q

percentage ionisation

A

percentage of an acid that has been ionised in water

[A-]/[HA] x 100

42
Q

pKa

A

pKa = -log10 Ka

smaller pKa corresponds to greater acid strength

43
Q

Kb

A

for B + H2O(l) BH+ + OH-

Kb = [BH+][OH-]/[B]

44
Q

relationship between Ka and Kb

A

Ka x Kb = Kw = 1.01x10^-14

45
Q

acid base techniques - winemaking

A

wine mainly contains tartaric acid, malic acid and citric acid and has a pH of about 2.5 to 4
back titrations are often used to find the alcohol content in wine

46
Q

acid base techniques - mining

A

need to know the composition of ores, metals and alloys

sample are dissolved in acid then titrated to find the composition

47
Q

acid base techniques - water treatment

A

both acids and bases are used to treat drinking water and waste water to ensure they have a pH of around 7
HCl is commonly used to lower the pH
Mg(OH)2 or NaOH used to raise the pH
neutralisation process prevents highly acidic or basic water flowing through pipes and corroding them

48
Q

Acid Base techniques by ATSI people

A

Soap Tree (Alphitonia Excelsa)

  • used by the Kuku Yalanji people of the Daintree
  • leaves contain saponins which tend to be acidic
  • the wood, bark and leaves contain many organic acids and small amounts of methyl salicylate
  • methyl salicylate is thought to be responsible for the analgesic properties of the plant
  • one end of the saponin molecule is hydrophilic while the other is hydrophobic, which explains its ability to act as a mild soap
  • used on the skin as a cleanser and as an antiseptic for treating rashes and ringworm
49
Q

buffers

A

maintain a pH within a certain range despite the addition of an acid or base
occurs in a conjugate acid base pair where the acid is weak

50
Q

ability of buffers

A

the ability of buffers to resist changes in pH depends on the conjugate acid/base

  • higher initial concentration of conjugate acid and base means a greater capacity for a buffer to resist changes to its pH
  • a buffer should have equal ability to resist changes from acids and bases
51
Q

blood buffers

A

blood needs to be in a pH range of 7.35 to 7.45

CO2 + H2O H2CO3
H2CO3 + H2O HCO3 - + H3O+

carbon dioxide converts into acid when dissolved in blood

52
Q

ocean buffer

A

ocean absorbs CO2 from atmosphere
CO2 + H2O H2CO3
H2CO3 + H2O HCO3 - + H3O+

ocean buffer systems are unable to combat the increase in CO2, increasing the oceans acidity

53
Q

cells buffers

A

cells need pH close to neutral
intracellular fluid contains phosphate buffer system
H2PO4 + H2O HPO42- + H3O+

HSC Chemistry (6 decks)

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