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Chemistry 2000 lab exam > Steps A - D potassium trioxalato ferrate tri hydrate > Flashcards

Steps A - D potassium trioxalato ferrate tri hydrate Flashcards

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1
Q

what are the three phases of a synthesis

A
  1. reaction
  2. workup
  3. characterization
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2
Q

describe the three phases of a synthesis

A

reaction
- identifying what parameters need to meet to have a successful experiment (like what are the reactants, what solvent is needed?)

workup
- some way to isolate the desired product from biproducts present

characterization
- qualitative and quantitative analysis to determine if we have made the correct product and HOW much

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3
Q

what is the limiting reagent in

2 H2 + O2 —> 2 H2O

A

oxygen is the limiting reagent

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4
Q

what is the chemical formula for ferrous oxalate hydrate

A

FeC2O4 x H2O

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5
Q

what colour is ferrous oxalate hydrate

A

yellow

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6
Q

what is an intermediate to the complex salt

A

ferrous oxalate hydrate

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7
Q

what is the formula for potassium trioxalato ferrate (iii) trihydrate

A
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8
Q

proper technique for diluting 18 M H2SO4 to 100 ml 3M H2SO4

A

v1c1 = v2c2
(0.1L)(3M) = x(18M)
V2 = 0.017 ml

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9
Q

is oxalic acid a liquid or solid under normal lab conditions

A

solid

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10
Q

is this reaction a reduction or oxidation

A

reduction (Mn)4 is gaining electrons)

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11
Q

how to calculate theoretical yield

A

actual yield from experiment / theoretical yield from product produced based on limiting reagent

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12
Q

what is the end point colour change of the permanganate-oxalate reaction

A

dark purple to light pink

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13
Q

why is potassium permanganate handled carefully

A

will leave brown spots on clothes or skin AND can irritate skin and eyes

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14
Q

what is the catalyst used in the permanganate-oxalate reaction

A

manganous ion (Mn2+)

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15
Q

what are the colour of the crystals in the final product

A

green

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16
Q

why did we analyze the final crystals

A

to determine the percent composition of each element in the crystals

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17
Q

what was the first step of preparing the Ferrous Oxalate (PART A)

A

quantitatively transferring the ferrous ammonium sulfate to a beaker charged with 25 ml of warm water and acidified with 20 drops of 3 M H2So4

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18
Q

what is the formula for Ferrous Ammonium Sulfate

A
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19
Q

how was the mass of Ferrous Ammonium Sulfate used determined (PART A)

A

after transferring to the prepared beaker the vial was rinsed with small amount of RO water and dumped into beaker

AFTER the vial was washed with acetone to evaporate the water and weighted

Subtract the vial with crystals from vial without

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20
Q

how was oxalic acid prepared (PART A)

A

2.5 grams of the oxalic acid with 25 ml of RO water

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21
Q

what do oxalic acid crystals need to fully dissolve (PART A)

A

gentle heating

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22
Q

where was the oxalic acid added (PART A)

A

to the Ferrous Ammonium solution

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23
Q

what was done once the oxalic acid was added to the ferrous ammonium solution (PART A)

A

the combined solution was brought to a gentle boil while stirring CONTINUOUSLY

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24
Q

what happens as the oxalic acid and ferrous ammonium solution was heated (PART A)

A

the precipitate at the bottom goes from a dark orange colour to more yellow as more ferrous oxalic forms

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25
Q

describe the steps of part A when the Buchner funnel was used

A

the clear supernatant liquid was decanted with a vacuum filtration system

the precipitate was washed with 25 ml of hot water and decanted again (discarding the liquid but keeping the solid)

third wash again with 25mL of hot RO water and transfer the ENTIRE precipitate to the filter paper in the Buchner funnel

final rinse with 25 ml of acetone

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26
Q

what was the LAST step in the preparation of the ferrous oxalate intermediate (PART A)

A

transferring the dry yellow crystals to a weighted 250 ml beaker and letting sit for the week

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27
Q

what was the objective of part A

A

aims to synthesize the intermediate compound (ferrous oxalate dihydrate) by heated combination of ferrous ammonium sulfate hexahydrate and oxalic acid dihydrate undergoing filtration with a vacuum apparatus

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28
Q

is potassium permanganate an oxidizing agent or reducing agent

A

oxidizing agent

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29
Q

is potassium permanganate reduced or oxidized in a reaction

A

reduced

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30
Q

what is the formula for potassium permanganate

A

KMnO4

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31
Q

what does potassium permanganate look liked reduced in BASIC OR NEUTRAL conditions

A

mixture of products results including SOLID MnO2 and green Manganate ion MNO4

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32
Q

what does potassium permanganate look like reduced in ACDICI conditions (half reaction)

A
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33
Q

what was the molarity of the potassium permanganate solution produced

A

0.02 M

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34
Q

what are safety precautions for bisulfite cleaning solution

A

irritant to the respiratory tract, eyes, mucous membranes and skin

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35
Q

how can the bisulfite cleaning solution be discarded

A

down the sink with lots of water

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36
Q

how much potassium permanganate was initially weighed to form 0.02 M solution

A

1.2 to 1.4 grams

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37
Q

what colour is potassium permanganate

A

black powder

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38
Q

what was the weighted potassium permanganate added to

A

a 600 ml beaker with 300 to 323 ml of water

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39
Q

what was done once the potassium permanganate was added to the water

A

heated to a gentle rolling boil

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40
Q

what was done once the potassium permanganate solution was heated to a gentle boil (FIRST TIME)

A

let sit with watch glass over and cool for FIVE minutes

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41
Q

what was done after the potassium permanganate solution was cooled

A

reheated to a gentle boil

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42
Q

what was done with the potassium permanganate solution after both boils and cooled

A

filtered through a funnel with glass wool positioned over a clean plastic bottle

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43
Q

how was a bottle cleaned for the potassium permanganate solution

A

10 ml of the bisulfite cleaning solution was poured into the bottle and let clean the bottle AND CAP before rinsing with RO water

44
Q

what was observed after the potassium permanganate was added to the water

A

the solution changed colour to a dark purple

45
Q

is the MNO4-/C2O4-2 reaction slow or fast at room temp

A

SLOW

46
Q

what was unique about the MNO4-/C2O4-2 titration

A

was carried out at elevated temps

47
Q

what increases the rate of the MNO4-/C2O4-2 titration

A

the production of the catalyst Mn2+

48
Q

what is the MNO4-/C2O4-2 titration reaction called

A

autocatalytic

49
Q

what is an autocatalytic reaction

A

a chemical reaction where one of the products of the reaction acts as a catalyst to speed up the reaction and produce more of itself

50
Q

what was added to the three Erlenmeyer flasks for the MNO4-/C2O4-2 titration

A
  1. 0.18 to o0.22 g of sodium oxalate
  2. 60 ml of RO water
  3. 10 ml of 3 M H2SO4
51
Q

what is the formula for sodium oxalate

A

Na2C2O4

52
Q

how was each MNO4-/C2O4-2 titration carried out

A

1, heat the contents of the flask between 80 to 90 degrees

  1. titrate the solution with KMNO4 solution
53
Q

describe the first few drops in the MNO4-/C2O4-2 titration

A

very SLOW to initiate the reaction

54
Q

what is the overall equation for the MNO4-/C2O4-2 titration

A
55
Q

potassium permanganate formula

A
56
Q
A

potassium permanganate

57
Q

sodium bisulfite

A
58
Q
A

sodium bisulfite

59
Q

ferrous ammonium sulfate hexahydrate

A
60
Q
A

ferrous ammonium sulfate hexahydrate

61
Q

oxalic acid dihydrate

A
62
Q
A

oxalic acid dihydrate

63
Q

ferrous oxalate dihydrate

A
64
Q
A

ferrous oxalate dihydrate

65
Q

balanced reduction reaction for MNO4-/C2O4-2 titration

A
66
Q

balanced oxidation reaction for MNO4-/C2O4-2 titration

A
67
Q

how to find molarity of KMnO4 for one trial of MNO4-/C2O4-2 titration

A
68
Q

what was done with the ferrous oxalate intermediate after it was dry

A

it was suspended in 30 ml of warm solution containing 3.5 g potassium oxalate

69
Q

what colour was the suspension after the ferrous oxalate intermediate was added to the potassium oxalate solution

A

dark orange/ rust colour

70
Q

how much H2O2 was measured out

A

10 ml into a graduated cylinder

71
Q

what were the steps and precautions taken when adding H2O2 to the solution with the ferrous oxalate intermediate and potassium oxalate solution

A

in an ICE BATH the H2O2 was added in SMALL increments (1ml increments) while stirring

72
Q

what was the result after H2O2 was added to the solution with ferrous oxalate intermediate and potassium oxalate solution

A

brown slushy solid

73
Q

what was the resulting brown slush made of (after H2O2 added to solution with the ferrous oxalate intermediate and potassium oxalate solution)

A

Fe(OH)3

74
Q

how was oxalic acid made for the second step of complex salt synthesis

A

1g oxalic acid to 10 ml of wate r

75
Q

what were the steps for adding the oxalic acid to the solution of ferrous oxalate intermediate, potassium oxalate solution and H2O2

A

add the first 7 ml and then heat to a gentle boil before adding the last 3 ml with an eye dropper

76
Q

what was done after the solution with the ferrous oxalate intermediate, potassium oxalate, oxalic acid, and h2o2 was heated together

A

filter through Buchner funnel

77
Q

after filtering through Buchner filter what was done to the second intermediate product of complex salt

A

15 ml of 95% ethanol

78
Q

how were the complex salt crystals harvested

A

filter with suction and wash crystals with 20 ml of EQUI-VOLUME ethanol and water

AFTER, rinse with 20 ml of acetone

79
Q

what happens to the final product as it is exposed to light

A

soon become covered with yellow powder (ferrous oxalate)

80
Q

is H2O2 an oxidizing agent or reducing agent

A

oxidizing agent

81
Q

is H2SO4 a strong or weak acid

A

strong

82
Q

safety precautions for H2SO4

A

corrosive and irritant to skin and causes severe burns

83
Q

safety precautions for H2O2

A

corrosive irritant to skin, eyes, mucous membranes

84
Q

objective for the second step in complex salt synthesis

A

take the previously produced ferrous oxalate dihydrate and using potassium oxalate and hydrogen peroxide form the final product potassium trioxalato ferrate (iii) trihydrate by the process of filtering through a Buchner funnel. AFTER the product has been allowed to sit in the dark the complex salt will form crystals due to recrystallization

85
Q

what colour did the brown sludge turn after the oxalic acid was added

A

green

86
Q

potassium oxalate monohydrate formula

A
87
Q
A

potassium oxalate monohydrate

88
Q

ethanol formula

A
89
Q
A

ethanol

90
Q

acetone

A
91
Q

potassium trioxalato ferrate (iii) trihydrate

A
92
Q

balanced equation for complex salt

A
93
Q

limiting reagent in the equation for complex salt

A

FeC2O4 x 2 H2O (ferrous oxalate dihydrate)

94
Q

how was percent water found in the green crystals (steps in experiment)

A
  1. weight 0.7 to 0.8 of the complex salt into evaporating dish (pre-weighted)
  2. place dish in the oven at 120 for 45 mins
  3. let cool
  4. weight to a constant mass
95
Q

how was percent oxalate found in the green crystals (steps in experiment)

A
  1. weight out three samples (0.18 to 0.22 g ) of complex salt into 3 Erlenmeyer flasks
  2. add 60 ml H2o and 10 ml 3 M H2SO4 to each flask
  3. heat ONE sample to 80 - 90 degrees before completing titration with KMnO4 until faint pink seen
96
Q

when is the titration with KMnO4 done (end point)

A

when a faint pink colour is seen

97
Q

how was percent iron found in the green crystals (steps in experiment)

A
  1. add 3ml 18 M H2SO4 to dried crystals in evaporating dish and cover with watch glass
  2. heat the contents in the dish for several mins on hot plate
  3. cool the contents in the fume hood
  4. pour ferric sulfate into Erlenmeyer flask and add 25 ml of RO water
  5. heat Erlenmeyer flask contents to boil
  6. add small proportions of zinc until the pale yellow solution turns clear
  7. filter through Whatman paper into clean flask and titrate with KMnO4
98
Q

when can zinc be added to the ferric sulfate

A

when the solution had turned a pale yellow colour from the cloudy solution

99
Q

what is the objective of the final stage in this synthesis

A

determine whether we have produced the correct product (potassium trioxalato ferrate (III) trihydrate) after the 2 previous phases and to determine we have the correct yield of the product

100
Q

what is the half reaction for Fe3+

A
101
Q

what is the half reaction for Zn

A
102
Q

what is the reaction between Zn and Fe3+

A
103
Q

what is the half reaction for MnO4-

A
104
Q

what is the half reaction for Fe2+

A
105
Q

what is the reaction between MNO4- and Fe2+

A
106
Q

how to calculate percent deviation

A

Chemistry 2000 lab exam (5 decks)

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