4) Acids and redox Flashcards

1
Q

Define strong acid

A

an acid that dissociates completely in solution

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2
Q

Define weak acid

A

an acid that dissociates only partially in solution

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3
Q

Define base

A

a compound that neutralises an acid to form a salt

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4
Q

Define alkali

A

a type of base that dissolves in water forming hydroxide ions

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5
Q

Define neutralisation

A

chemical reaction in which an acid and a base react together to form a salt

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6
Q

acid + metal oxide / hydroxide / alkali ->

A

salt + water

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7
Q

acid + metal carbonate ->

A

salt + water + carbon dioxide

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8
Q

Define titration

A

a technique to accurately measure the volume of one solution that reacts exactly with another solution

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9
Q

Give 3 purposes of carrying out a titration

A

finding the concentration of another solution
identification of unknown chemicals
finding the purity of a substance

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10
Q

What piece of apparatus can be used to make up a standard solution?

A

a volumetric flask

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11
Q

Define standard solution

A

a solution of known concentration

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12
Q

Give the 5 steps to prepare a standard solution

A
  1. weigh solid
  2. dissolve solid in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark
  3. transfer to volumetric flask, rinsing last traces of solution into the flask with distilled water
  4. carefully fill to graduation line (bottom of meniscus) dropwise with distilled water at eye-level
  5. invert several times to mix
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13
Q

Give a method for an acid-base titration procedure

A
  1. add a measured volume of one solution to a conical flask using a pipette
  2. add the other solution to a burette and record the initial burette reading
  3. add a few drops of indicator to the conical flask
  4. run the burette solution into the conical flask swirling throughout. the indicator changes colour at the end point (indicates when the volume of 1 solution reacts exactly with the volume of the second solution)
  5. record the final burette reading
    A quick, trial titration is carried out first to find the approximate titre. The titration is then repeated accurately, adding the solution dropwise as the endpoint is approached. Further titrations are carried out until two accurate titres are concordant.
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14
Q

Define titre

A

the volume added from the burette when the volume of one solution has exactly reached with the solution

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15
Q

Define concordant

A

agree to within 0.10cm^3

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16
Q

The mean titre should only include _?

A

the two concordant titres

17
Q

How do you calculate a titre value?

A

subtract the initial from the final burette readings

18
Q

What can a titration be used for?

A

identification of a carbonate

19
Q

Define oxidation number

A

a measure of the number of electrons than an atom used to bond with atoms of another element

20
Q

The oxidation number for elements is always _?

A

zero

21
Q

Oxidation number for O as a combined element?

A

-2

22
Q

Oxidation number for H as a combined element?

A

+1

23
Q

Oxidation number for F as a combined element?

A

-1

24
Q

Oxidation number for Na+ / K+ as a combined element?

A

+1

25
Q

Oxidation number for Mg2+ / Ca2+ as a combined element?

A

+2

26
Q

Oxidation number for Cl- / Br- / I- as a combined element?

A

-1

27
Q

Oxidation number for H in metal hydrides e.g. NaH?

A

-1

28
Q

Oxidation number for O in peroxides e.g. H2O2?

A

-1

29
Q

Oxidation number for O bonded to F e.g. F2O?

A

+2

30
Q

Sum of oxidation numbers = _?

A

total charge

31
Q

Roman numerals are used in the names of compounds of elements that form _?

A

ions with different charges

32
Q

The Roman numeral shows the _?

A

oxidation state

33
Q

Describe iron (II)

A

Fe2+ with the oxidation number +2

34
Q

Describe iron (III)

A

Fe3+ with the oxidation number +3

35
Q

Describe nitrate (III)

A

nitrite; NO2- with the oxidation number +3

36
Q

Describe nitrate (V)

A

nitrate; NO3- with the oxidation number +5

37
Q

Define redox reaction

A

a reaction involving reduction and oxidation

38
Q

Define reduction

A

removal of oxygen / gain of electrons / decrease in oxidation number

39
Q

Define oxidation

A

addition of oxygen / loss of electrons / increase in oxidation number