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Chemistry > Mod. 6 > Flashcards

Mod. 6 Flashcards

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1
Q

What did Lovoiser suggest?

A
  • An acid contains oxygen
  • Non-metal oxides react with water to form acidic solutions
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2
Q

What did Darvy suggest?

A
  • Acids contain hydrogen
  • Metal oxides = bases
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3
Q

What was Arrhenius’s proposal?

A

Acids produce H+ ions in water and bases produce OH- ions in water, in aqueous solutions
- Arrhenius explained neutralisation

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4
Q

What were the limitations of Arrhenius’s proposal?

A
  • Could not explain why certain compounds do not contain hydroxide ions, despite displaying basic properties, e.g. 2HCI + CaCO3 → CaCl2 + H2O + CO2 [calcium carbonate is basic but doenst contain OH]
    -Could not explain acid-base reaction that do not occur in aqueous solutions, e.g.
    NH3(g)+ HCI(g)→ NH4Cl(s)
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5
Q

What did Bronsted Lowry’s proposal?

A
  • acid donates H+ protons
  • bases accept H+ protons
  • acids have high concentrations of H+
  • bases have lower concentrations of H+
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6
Q

What were the limitations of B-L theory?

A
  • Doesn’t explain the acidity of acidic oxides ( SO2)/ basicity of basic oxides ( MgO)
  • Doesn’t explain reaction between acidic and basic oxides that don’t involve proton transfer, e.g. SO3(g)+ CaO(s)→ CaSO4(s)
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7
Q

What’s an inorganic acid?

A

a substance with an ion attached to 1 or more hydrogen

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8
Q

What’s an inorganic base?

A

a substance that releases OH- in solutions

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9
Q

What’s the equation for acid-carbonate reactions?

A

carbonate + acid –> salt + carbon dioxide + water

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10
Q

Provide an example of an acid-carbonate reaction.

A

2HI(aq) + Na2CO3 –> NaCl ( aq) + CO2( g) + H20 (l)

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11
Q

What’s the equation for acid-metal reactions?

A

acid + metal hydroxide –> salt + water

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12
Q

Provide an example of an acid-metal reaction.

A

Na(s) + HCI( aq) –> NaCl (aq) + 1/2 H20(l)

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13
Q

What does neutralisation mean?

A

when the concentration of hydronium and hydroxide ions becomes equal

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14
Q

What’s the equation for a neutralisation reaction?

A

acid + base → salt + water

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15
Q

Provide an example of a neutralisation reaction.

A

NaOH(aq) + HNO3(aq) –>Na NO3(aq)+H2O(l)

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16
Q

Name 3 strong acids

A

HCI, H2SO4, HNO3

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17
Q

Name 3 weak base.

A

CH3COOH, H2CO3, H3PO4

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18
Q

Name 3 strong bases.

A

NaOH, KOH, H3PO4

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19
Q

Name 3 weak bases

A

NH3, C5H5N, CH3NH2

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20
Q

Define hydrolysis.

A

the reaction of a salt with water that results in a pH change

21
Q

Explain the hydrolysis of acidic salts.

A

acidic salts contain conjugate acids of weak bases which hydrolise to produce acidic solutions.

22
Q

Explain the hydrolysis of basic salts

A

basic salts contain conjugate bases of weak acids which hydrolise to produce an alkaline

23
Q

Explain the hydrolysis of neutral salts

A

typically formed from the neutralisation between strong acids and strong bases ( do not hydrolyse)

24
Q

What happens to the volume and concentration when diluted?

A

the volume increases and the concentration decreases

25
Q

What happens to the pH during dilution?

A
  • for acids the pH increases
    -for bases the pH decreases
26
Q

What is a primary standard?

A

a solution that is prepared using chemicals that are pure that are used o prepare a solution accurately of known concentration

27
Q

What are the properties of a primary standard?

A
  • high level of purity
  • free of moisture
  • stable and unaffected by air during weighing
28
Q

What are examples of some primary standards? Provide an acid and a base.

A
  • potassium hydrogen phthalate ( acid)
  • sodium carbonate ( base)
29
Q

What are two examples of non-primary standards?

A
  • Sulfuric acid→ absorbs water from the atmosphere
    -Sodium hydroxide → absorbs moisture from the air
30
Q

Define the word titration.

A

volumetric analysis used to determine the concentration of an unknown solution

31
Q

Define endpoint

A

the point at which the colour of the indicator changes

32
Q

Define equivalence point

A

the point at which enough titrant has reacted with all the substances that the experiment comes to an end

33
Q

If initial pH is below 2 the curve indicates its a…

A

strong acid

34
Q

If the initial pH is 4-7 the curve indicates its a…

A

weak acid

35
Q

If initial pH is 10 or 11 the curve indicates its a…

A

weak base

36
Q

if initial pH is higher than 13 the curve indicates its a…

A

strong base

37
Q

Why do weak acid + weak base titrations not work?

A

they don’t have a clear indication of the equivalence point as there is no shape rise around the equivalence point

38
Q

What indicator is used for strong acids/ strong bases? Describe the colour change.

A

Bromyothyl blue. When acidic turns yellow when basic turns blue.

39
Q

Methyl Orange turns red to yellow. What acid and base is this applied to?

A

Strong acid/ weak base

40
Q

What indicator is used for strong base/ weak acid titrations? Describe the colour change.

A

Phenolphthalein it changes from colourless ( acidic) to pink (basic)

41
Q

What’s the substance used to rinse the conical flask? Justify your answer.

A

distilled water → doesn’t leave residue chemicals that can affect the measurements

42
Q

What’s the substance used to rinse pipettes? Justify your answer.

A

distilled water, then with the solution they will measure and transfer → ensures that any water or solution from previous use is completely removed.

43
Q

Define diprotic.

A

diprotic means the substance has 2 acidic hydrogen protons.

44
Q

What’s the difference in pH between a monoprotic and diprotic substance?

A

Diprotic substances will have a lower pH. This is because when diprotic substances ionise, they produce a higher concentration of hydrogen ions, compared to monoprotic ones.

45
Q

Why is it important during titrations to keep the amount of indicator added to a minimum?

A
  • Addition of large amount of indicator can change H+ concentration
  • Can change the equivalence point or the accuracy/ validity of reading
  • Weak acid and conjugate base can absorb or release H+ ions resulting in addition of acid or base
46
Q

What’s the formula for indicators?

A

Hln –> H + In

47
Q

How do indicators impact the equilibrium of an acid?

A

when an acid is added, [H+] increases, equilibrium shift to the left

48
Q

How do indicators impact the equilibrium of a base?

A

when a base is added OH- bonds with H+ to form H20. As [H+] decrease, the equilibrium shifts to the right

Chemistry (3 decks)

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