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chemistry > module 6 HSC > Flashcards

module 6 HSC Flashcards

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1
Q

properties of acids

A
  • sour taste
  • burn skin
  • blue litmus to red
  • pH < 7
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2
Q

properties of bases

A
  • bitter taste
  • soapy feel in aqueous solution
  • red litmus to blue
  • pH > 7
  • caustic
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3
Q

acid + base

A

salt + water

HNO3 + NaOH –> H2O + NaNO3

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4
Q

acid+ carbonate

A

salt + water + carbon dioxide

2HCl (aq) + Na2CO3 (s) –> CO2 (g) + H2O (l) + 2NaCl(aq)

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5
Q

acid + active metal

A

salt + hydrogen gas

H2SO4 (aq) + Ba(s) –> H2 (g) + BaSO4(s)

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6
Q

what are indicators

A

substances which change colour based on the pH of the environment
- methyl orange (orange)
- bromthymol blue (green)
- phenolphthalein (pink)

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7
Q

methyl orange

A

3.1 - 4.4

red - orange - yellow

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8
Q

bromothymol blue

A

6.0 - 7.6
yellow - green - blue

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9
Q

phenolphthalein

A

8.3 - 10.0
colourless - pale pink - pink/magenta

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10
Q

natural indicator

A

red cabbage

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11
Q

antoine lavoiser

A

acids contain O
bases neutralise acids

a: raised the need to define acids and bases
d: statement is wrong eg. HCl

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12
Q

humphrey davy

A

Acids contain replaceable H. Bases neutralise acids.

a: worked for many acids
d: cannot explain acidic or basic oxides

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13
Q

arrhenius

A

acids release H+ in solution and bases release OH - in solution
a:
- works for many acids and bases
- explains the common mechanism of acid base neutralisations

d:
- does not recognise solvents in determining the acidic/weakness of acid
- cannot explain basic nature of carbonates, acidic or basic salts in not aqueous form

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14
Q

bronsted lowry

A

acids donate protons, bases accept protons

a:
- recognises role of solvent in determining the strength and weakness of an acid
- explains acidic and basic behaviour in non aqueous solvents
- explains how species can be amphiprotic
- recognises conjugate acids and bases

d:
- cant explain amphoteric substances
- cannot explain acids or bases that dont accept/donate protons

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15
Q

amphoteric substances

A

can act as both an acid or base

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16
Q

amphiprotic

A

can act as either an acid or base in different chemical environments

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17
Q

enthalpy of neutralisation

A

thermal energy change

q = mcat
delta h = -q/n

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18
Q

proticity + what is a protic substance

A

capacity to act as a proton donor
eg. mono HCl, diprotic H2SO4, triprotic H3PO4

  • strong is the first (one directional arrow) , weak is the scond (biodirectinal arrow)
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19
Q

degree of ionisation

A

how much it ionises
strong acid: fully ionises 100%
weak acid: does not fully ionise <100%

[A-]eq / [HA] initial x 100%

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20
Q

strong acid degree of ionisation

A

100

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21
Q

weak acid degree of ionisation

A

<100

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22
Q

strong acids

A

HCl, HBr, HI, HNO3, H2SO4 (first is strong, second is weak)

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22
Q

strong bases

A

HF, CH3COOH, H2CO3, H3PO4, C6H8O7

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23
Q

conjugate of base HSO2-

A

acid H2SO4

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24
Q

conjugate of acid HCl

A

base Cl-

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25
Q

conjugate of strong …

A

extremely weak/almost neutral

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26
Q

conjugate of weak …

A

weak

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27
Q

conjugate of extremely weak …

A

strong

28
Q

prove that HCO3 from NaCO3 is amphiprotic

A

strong base : …
strong acid: …

29
Q

neutralisation

A

acid base reaction that goes to completion and does not directly produce H3O+ and OH-

  • strong goes to completion
  • weak does not go to completion

explain with both le chateliers and bronsted lowry

eg. CH3COOH weak acid in water
- NaOH strong base in water

CH3Cooh + NaOH -> NaCh3CH3COOH + H2O

  • since acetic acid is a weak acid relative to water but strong acid relative to sodium hydroxide and sodium hydroxide is a strong base relative to water and acetic acid is stronger than water –> the acetic acid will ionise completely in the presence of sodium hydroxide where neutralisation is complete
30
Q

changing degree of ionisation

A

depends on concentration acids however only temperature changes the Ka

31
Q

pH

A

-log10[H3O+]

32
Q

[H3O+]

A

10^-pH

33
Q

factors that affect an acids pH

A
  1. concentration
  2. strength
  3. proticity (strong acids)
  4. degree of ionisation (weak acids)
34
Q

concentration impacts on pH

A

more concentrated acid = lower pH
think about how a log is an inverse

35
Q

strength impact on pH

A

strong acids have a lower pH as it completely ionises in water

36
Q

proticity impact on pH

A

strong acids only
higher proticity = lower pH
sulfuric acid has a lower pH than HCl as it has both a strong first ionisation and weak second ionisation

37
Q

degree of ionisation impact on pH

A

weak acids only
high degree of ionisation = lower pH
citric < acetic < carbonic

  • although carbonic acid has more protons readily available to donate, it has a much lower degree of ionisation
38
Q

what salt does strong acid + strong base produce

A

neutral salt

39
Q

what salt does strong base + weak acid produce

A

acidic salt

40
Q

what salt does strong acid + weak base produce

A

basic salt

41
Q

what salt does weak acid + weak base produce

A

any of them..?

42
Q

what is the levelling effect of a solvent

A

acid: strength of acid is levelled/limited by the ability of a solvent to accept protons
base: strength of base is levelled by the ability of solvent to donate protons

43
Q

define titration

A

volumetric analysis which the concentration of a solution is determined by measuring the volumes of solutions involved in a reaction
- uses neutralisation reactions

44
Q

equivalence point

A

point at which equal moles of H3O+ ions and OH- ions have been reacted together

45
Q

endpoint

A

the point at which a sustained colour change is achieved using an appropriate indicator

46
Q

titration error

A

the difference between the equivalence point and the endpoint

47
Q

titre

A

the minimum volume required to reach the endpoint of the neutralisation reaction in the titration

48
Q

titrant

A

solution which is used to determine the concentration of an unknown solution

49
Q

analyte

A

solution whose concentration is to be determined

50
Q

standard solution

A

solution with known concentration

51
Q

qualities looked for in a standard solution (primary standard) + example

A
  • high purity
  • stability in air
    -high molecular weight
  • inexpensive and readily obtained

eg.

acid: hydrated oxalic acid (weak acid for strong base)

base: anhydrous sodium carbonate (Na2CO3) / sodium hydrogen carbonate (NAHCO3) -> weak base for strong acid

52
Q

what to avoid in a primary standard

A

weak acid and weak base together

deliquescent compounds: absorb water from surrounding environment by reacting with CO2 in air which dissolves in the solution eg. NaOH + KOH

hydroscopic: attract water molecules due to the presence of hydrophilic groups eg. H2SO4

53
Q

what is al the glassware rinsed with

A

all glassware rinsed with demineralised water first

pipette + burette = rinsed finally with solution they are to contain to ensure the concentration of substances they are to contain are accurate
(the demin water would dilute the solution)

volumetric flask + conical flask = rinsed thoroughly with demineralised water so the number of moles of the substance can be accurate

54
Q

beaker

A

used to dissolve the dry powdered primary standard to make the standard solution

55
Q

volumetric flask

A

cleaned with demin and and filled to the gradation line with the standard solution then inverted 20 times to homogenise the solution

56
Q

FIX TITRATION FLASH CARDS

A
57
Q

neutralisation real life applications

A

antacid tablets:
- antacid tablets contain Mg(OH)2/Al(OH)3 that undergo neutralisation with excess gastric acid in the human stomach eg HCl

tooth decay:
- acids from food and drinks cause tooth decay
- toothpaste is weakly alkaline with undergoes neutralisation with acids present on the cavity
- CaCO3

baking:
- sodium bicarbonate (NaHCO3) (s)
- reacts with acids
- gives cake airy quality and produces CO2 to help rise

industrial:
- sodium hydrogen carbonate is used to neutralise any spills that are acidic.basic that is corrosive and causes harm to the environment and should e cheap, safe and weakly acidic/basic

wastewater:
treatment of waste water
- HF used to neutralise NaOH and Ca(OH)2 and produces a solid that can be removed

58
Q

antacid tablets

A
  • antacid tablets contain Mg(OH)2/Al(OH)3 that undergo neutralisation with excess gastric acid in the human stomach eg HCl
59
Q

baking

A
  • sodium bicarbonate (NaHCO3) (s)
  • reacts with acids
  • gives cake airy quality and produces CO2 to help rise
60
Q

tooth decay

A
  • acids from food and drinks cause tooth decay
  • toothpaste is weakly alkaline with undergoes neutralisation with acids present on the cavity
  • CaCO3
61
Q

industrial

A
  • sodium hydrogen carbonate is used to neutralise any spills that are acidic/basic that is corrosive and causes harm to the environment and should e cheap, safe and weakly acidic/basic
62
Q

waste water

A

treatment of waste water
- HF used to neutralise NaOH and Ca(OH)2 and produces a solid that can be removed

63
Q

styrofoam cup experiment

A
  • imperfect insulator = heat loss ot the environment -> use styrofoam lid
  • thermometer should not touch the bottom of the cup as the reading will be wrong
64
Q

Kw

A

10^-14 = Ka x Kb

65
Q

pH + pOH

A

14

66
Q

define a buffer

A

similar/comparable concentrations of a weak acid/base and its conjugate which resists the change in pH if another acid/base is added

67
Q

how do buffers work

A

eg. carbonic acid (wa) is mixed with sodium hydrogen carbonate
H2CO3/HCO3- system

  • then write the equations showing the addition of H3O+ and addition of OH-

addition of H3O+: acid
- acid consumed by HCO3- shifting the equation to the left to reduce [H3O+] by LCP
- minimal change in [H3O+] , pH remains stable

addition of OH-: base
- base consumed and shifts left to decrease [OH-] by LCP

then link back to buffer: therefore since the solution minimises changes in [OH-] and [H3O+], it can act as a buffer

68
Q

example of buffers

A

human blood:
- to maintain homeostasis

acidic through exercise as more carbonic acid is produced:
- shifts left to increase H2CO3

ocean buffer:
HCO3-/CO32- buffer system
- shells and limestone composed of CaCO3 that dissolve into CO32-

chemistry (9 decks)

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