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Fall 2022 > Chemistry Lab > Flashcards

Chemistry Lab Flashcards

1
Q

What is a hydrate?

A

a hydrated compound that has a specific number of water molecules associated with in as part of the CRYSTAL STRUCTURE

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2
Q

What is oxalate?

A

C2O4

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3
Q

What is oxalic acid?

A

H2C2O4*2H2O - oxalate bonded to 2 water molecules with hydrogen bonding

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4
Q

What is copper sulphate pentahydrate? How are the water molecules bonded?

A

CuSO4*5H2O - blue solid - 5 H2O molecules COORDINATED to the Cu and SO4 coordinated to sulphate

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5
Q

What is anhydrous copper sulphate?

A

CuSO4 - no water molecules - white solid

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6
Q

What could happen when hydrated solids are heated?

A
  1. decompose

or

  1. some or all water molecules removed
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7
Q

What are the conditions necessary to calculate the mass percent of water removed from a hydrated solid?

A

water molecules removed without decomposition and solid is at a constant mass

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8
Q

What is density dependant on for solid and liquids? Gases?

A

Solids and liquids – temperature

gases – temperature and pressure

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9
Q

How is density measured for solids & liquids? Gases?

A

solids and liquids – g/mL

gases – g/L

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10
Q

What is the formula for density?

A

D=m/V (mass/volume)

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11
Q

How do you calculate the mass of water removed?

A

initial mass of sample - final mass of sample

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12
Q

How do you calculate the % of water removed from a hydrated salt?

A

mass of water removed/initial mass of sample x 100

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13
Q

Why is it important to have a sample that was heated return to room temperature?

A

heat creates air currents that destabilize the balance pan = inaccurate mass measurement

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14
Q

Which type of weighing scale is more accurate?

A

analytic balance (compared to top loading)

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15
Q

What observations are seen when the hydrated salt is heated?

A

condensation on the inside of the glass; water vapour shown as bubbles

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16
Q

What is Potassium Trioxalatoferrate (III) trihydrate?

A

K3[Fe(C2O4)3)]*3H2O - coordination compound

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17
Q

What are the components of a coordination complex?

A

central METAL atom/ion bonded to two or more LIGANDS

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18
Q

What is a coordination compound?

A

A NEUTRAL substance that contains a coordination complex

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19
Q

What is the difference between a coordination compound and coordination complex?

A

compound - CATIONIC, ANIONIC, NEUTRAL

complex - contains compound and NEUTRAL

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20
Q

What is Ferrous ammonium sulphate hexahydrate?

A

(NH4)2Fe(H2O)62 - coordination compound

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21
Q

What is the coordination complex in (NH4)2[Fe(H2O)6(SO4)2?

A

[Fe(H2O)6]^2+

–> cationic

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22
Q

How are the water molecules bonded in the [Fe(H2O)6]^2+ complex? What does that mean for reactions?

A

H2O weakly bonded to Fe with hydrogen bonds that can be REPLACED by stronger bonding groups LIKE OXALATE ION

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23
Q

What is Iron (II) oxalate dihydrate?

A

Fe(C2O4)*2H2O - water molecules attached to Fe and oxalate ions bridge two water molecules (low solubility)

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24
Q

What is the purpose of of oxalic acid when reacting with ferrous ammonium sulphate hexahydrate?

A

oxalate ions will replace water molecules to produce iron (II) oxalate dihydrate (yellow insoluble compound)

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25
Q

After oxalic acid and ferrous ammonium sulphate hexahydrate have reacted what are the products?

A

iron (II) oxalate dihydrate

water molecules

ammonium hydrogen sulphate

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26
Q

Why must the solution be decanted?

A

remove excess liquid (composing of ammonium hydrogen sulphate and mainly water)

more water = larger solution volume = lower yield

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27
Q

What excess reagents are added to Ion oxalate dihydrate (Fe(C2O4)*2H2O) to produce Potassium trioxalatoferrate (III) trihydrate?

A

excess hydrogen peroxide -H2O2 - (oxidize)

excess potassium orate monohydrate

excess oxalic acid dihydrate

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28
Q

Once the reagents are added what is done to the solution? why? What is the issue with the product)

A

heated to remove excess reagent (but potassium trioxalatoferrate (III) trihydrate is still soluble in water)

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29
Q

What is added and done to the potassium trioxalatoferrate trihydrate to remove water?

A

ethanol added to help precipitate and filter the product. Buchner filter is used.

solution is also placed in an ice bath because solubility is low in cold temperatures

30
Q

What is the limiting reagent?

A

substances that runs out first (determines maximum amount of product that could be made - theoretical yield)

31
Q

What is the percent yield?

A

actual yield/theoretical yield x 100

32
Q

What is quantitative analysis?

A

determining the AMOUNT of a specific component in some sample

33
Q

What is GRAVIMETRIC analysis?

A
  • type of quantitative analysis
  • finding the change in mass associated with a chemical or physical process (ex. mass % of water removed from hydrated salt)
34
Q

What is a VOLUMETRIC ANALYSIS?

A
  • type of quantitative analysis
  • measuring the VOLUME of a SOLUTION required to react completely with another substance (ex. titration)
35
Q

What is the TITRATION process?

A
  • type of volumetric analysis
  • a STANDARD SOLUTION (of accurately known concentration) is gradually added to a known AMOUNT of ANALYTE (unknown solution) until all the analyze has reacted (EQUIVALENCE POINT)
36
Q

Why is an indicator necessary in a titration?

A

provides colour change once the endpoint of the reaction is reached due to concentration changes

37
Q

What is lithification?

A

imprints of shells that were compacted to make stone

38
Q

What occurs to carbonate compounds under acidic conditions?

A

production of CO2

CaCO3 + H2SO4 –> CaSO4 + CO2 + H2O

–> limestone dissolves

39
Q

What is HARDNESS? What is used for its calculations?

A

amount of Ca and Mg dissolved in water in ppm
–> all calcium and magnesium species are treated as calcium carbonate

40
Q

How can you calculate the harness in ppm?

A

mass of solute (mg)/mass of solution (kg)

or mass of solute (g)/mass of solution (g) x10^6

41
Q

How can you calculate hardness for CaCO3 in water?

A

mass of CaCO3 in mg/volume of water in L

42
Q

How do ligands act as Lewis bases?

A

react with metal cations (Lewis acids) to donate electron pairs

43
Q

What is a monodentate ligand? What is a chelating ligand? How do they compare in bond strength?

A

monodentate ligand - has ONE ATOM that donates the electron pair

chelating ligand - has TWO or MORE ATOMS that donate the electron pair

chelating ligands bond to metal ions TIGHTLY and can easily DISPLACE monodentate ligands

44
Q

What is Calmagite?

A

indicator that is a bidentate ligand ( O and O) forming a coordination complex with Mg2+
–> creates red coloured complex when its bond with Mg2+ is displaced by EDTA

45
Q

What is acid digestion?

A

carbonate salts reacting with acids to release CO2

46
Q

What are the insoluble materials when reading dolomitic limestone and oyster shells with acids?

A

insoluble non-carbonate materials (carbonate materials ARE soluble)

47
Q

What is the carbonate material in dolomitic limestone?

A

dolomite: CaMg(CO3)2

48
Q

What is the carbonate material in oyster shells?

A

CaCO3

49
Q

Why is there a change in mass in acid digestion?

A

loss of CO2 gas – now can determine the mass percent of CARBONATE SALT in the sample (limestone and oyster shell)

50
Q

What is the dolomitic limestone reaction with acid?

A

MgCO3 + CaCO3 + 4HCl –> CaCl2 + MgCl2 + 2CO2 + 2H2O

  • magnesium and calcium carbonate with hydrochloric acid produces soluble salts calcium and magnum chloride and CO2
51
Q

What is the oyster shell reaction with acid?

A

CaCO3 + 2HCl –> CaCl2 +CO2 + H2O

  • calcium carbonate with hydrochloric acid
52
Q

Why are the oyster shells and limestones crushed?

A

increases surface area = increases reaction rate

53
Q

Why is potassium borate buffer added to each titration flask?

A

maintain pH near 10 for EDTA and Calmagite indicator to bond to metal ions

54
Q

What does the reaction look like when indicator is added at the start with the sample?

A

Ca2+ + Mg2+ +In3- –> Ca2+ + MgIn- (red)

–> indicator bonds with Mg more strongly producing a red colour

55
Q

What does the reaction look like when EDTA is added initially?

A

Ca2+ MgIn- (red) + EDTA4- –> Ca[EDTA)]2- + MgIn-

–> EDTA first starts bonding with Ca more strongly

56
Q

What happens when more EDTA is added?

A

Indicator is displaced and EDTA bonds with Mg

Then hydrolysis reaction occurs between displaced Indicator and H2O: which produces the blue endpoint colour:

In3- (colourless) + H2O –> HIn2+ (BLUE) + OH-

57
Q

What is the identification of a gas test? Example?

A

heating a solution to identify the species present
–> reaction between NH4+ (ammonium ion) and sodium hydroxide (NaOH) produces gaseous ammonium (NH3) when heated – weak base causes red litmus paper to turn blue

58
Q

What is the flame test?

A

ALL elements emit light of a characteristic COLOUR when heated

  • heat energy excites an electron in an atom to a higher energy level
  • electron returns to a lower energy level and this energy is given off as light
  • since different elements have unique energy levels different elements produce different colours of light
  • element can be identified id the frequency of light is in the visible spectrum
59
Q

What is a precipitation reaction?

A

two AQUEOUS species react and an INSOLUBLE product is formed

60
Q

How can precipitate be observed?

A

crystals or cloudy due to solid
– colour is important (ex. silver chloride is white but silver bromide is beige) - transition metals are strongly coloured

61
Q

What is a solution?

A

homogenous mixture (all species are in the same phase or state) with no precipitate

62
Q

What is a heterogeneous mixture?

A

two phases present (ex. precipitate in liquid)

63
Q

What is suspension? What is a colloid?

A

suspension - precipitate that eventually settles
colloid - precipitate do not settle

64
Q

What does the flame experiment test for? What are the results?

A

butane torch used and observe initial colour
- Sodium – bright orange-yellow light
- Lithium – red-maroon light
- Potassium – pale purple light

65
Q

What does the sodium hydroxide and aqueous ammonia solution test for?

A

Transition metals-first add NaOH to create metal+hydroxide then add NH3

Copper (II) - blue solution
Zinc 2+ - colourless solution
Aluminum 3+ - insoluble white solid + no ammonium reaction
Iron II - insoluble green solid
Iron III - brown solid

66
Q

How was the Bromide and Iodide Ions tested for?

A

chloride water added to Br and paraffin oil is added so upper layer colour is orange

chlorine water addd to I- and paraffin oil is added so upper layer is purple

67
Q

How is the Sulphate Ion tested for?

A

unknown + barium which is INSOLUBLE in an acidic solution, so HCl is added

68
Q

How is the Carbonate Ion tested for?

A

unknown solution + HCl creates CO2 seen as small bubbles

69
Q

How is Chloride and Fluoride tested for?

A

unknown + AgNO3 –> AgCl creates a white solid (chloride test)

unknown + Ag –> no reaction (fluoride test)

70
Q

How is phosphate ion tested for?

A

phosphate ion forms a yellow precipitate with ammonium molybdate

Fall 2022 (12 decks)

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