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Chemistry (Tara) > Volumetric Analysis > Flashcards

Volumetric Analysis Flashcards

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1
Q

What does the moles of solute after dilution equal?

A

The moles of solute before dilution

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2
Q

What do you change and not change when you add water and dilute the solution?

A
  • change concentration

- do not change the moles of solute

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3
Q

What can colour intensity be measured by?

A

Using a colorimeter

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4
Q

What does the colour intensity dependent on?

A

The concentration of the solution

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5
Q

Define standard solution

A

A standard solution of know concentration

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6
Q

Define primary standard

A

A primary standard is a substance (solute) that can be made up to a standard solution directly as it is available in 100% purity, is stable in air, has a high molar mass of accuracy in weighing and dissolves easily in water.

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7
Q

Is a titration always needed to find a concentration?

A

No

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8
Q

What are the only two examples of primary standards that are used in the syllabus?

A
  • Anhydrous Na2CO3 (base), ammonium iron

- Sulphate (reducing agent)

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9
Q

Define secondary standard

A

A secondary standard is a substance(solutes) that cannot be made up to a standard solution directly as it is not available in 100% purity, or is not stable in air, or has a low molecular mass and does not dissolve readily in water

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10
Q

Define standardise

A

To standardise is to find out the concentration of a solution by titration or colorimetry

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11
Q

What is the first step in preparing a solution?

A

Solute (if solid is weighed accurately on a clock glass using an electronic balance.

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12
Q

What happens after the solute is weighed accurately on a clock glass?

A

All of the solute is transferred to a volumetric flask and made up to an accurately known volume e.g 250cm3

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13
Q

Why is the solute made up to an accurately known volume?

A
  • so the concentration can be calculated

- so there is enough solution to carry out 3 titrations

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14
Q

What happens first to the solute if it is solid?

A

Tipped into a beaker

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15
Q

What is the clock glass washed with?

A

Deionised water from a wash-bottle

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16
Q

What happens after the clock glass is washed with deionised water?

A

The rinsings are added to the beaker and stirred with a clean dry glass rod until it dissolves

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17
Q

What happens after the rinsings are added to the beaker?

A

The solution is poured into the volumetric flask with the aid of a funnel to prevent spillage

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18
Q

What happens after the solution is added to the volumetric flask?

A

The funnel is removed and deionised water is added to the flask until the level of the solution is 1cm3 below the mark on the neck of the flask

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19
Q

When do you stop adding the deionised water drop by drop to the volumetric flask?

A

Until the bottom of the meniscus is on the graduation mark and read at eye-level

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20
Q

What does the solution in the flask have after the deionised water is added?

A

A concentratinon gradient

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21
Q

What is done near the end to make the solution homogenous?

A

The flask is stoppered, inverted 20-30 times and shaken to make the solution homogenous

22
Q

Why does the volumetric flask have a narrow neck?

A

To make the measurement accurate and able to see the bottom of the meniscus clearly.

23
Q

What is used to measure out an exact volume if the solute is in liquid form (bleach or vinegar)?

A

A properly rinsed pipette

24
Q

How is the solute transferred to the volumetric flask if its in liquid form?

A

By touching the tip of the inside of the volumetric flask

25
Q

What is the apparatus needed to prepare a standard solution of sodium carbonate? (not a titration)

A
  • Safety glasses
  • 250cm3
  • Volumetric flask
  • Beaker
  • Funnel
  • Glass rod
  • Dropper
  • Electronic balance
  • Wash bottle
26
Q

Materials needed to prepare a standard solution of sodium carbonate? (not a titration)

A
  • 2.65g of sodium carbonate

- Deionised water

27
Q

volumetric analysis

A

reacting 2 solutions together to find the concentration of one of them

28
Q

to find the concentration what information do you need to have

A

amount of solute

amount of solution

29
Q

pwv or %w/v

A

percentage weight per volume

grams per 100 cm cubed

30
Q

pww or %w/w

A

grams per 100 cm cubed

31
Q

pvv or %v/v

A

cm cubed per cm cubed

32
Q

ppm

A

parts per million

milligrams per litre

33
Q

M

A

molarity

moles per litre

34
Q

why is the pipette used for solutions at room temperature only?

A

liquids expand on heating and contract on cooling

35
Q

how do you clean the pipette?

A

first with deionised water and then the solution that it will contain

36
Q

what do you use to fill the pipette

A

a pipette filler

37
Q

why do you use a pipette filler

A

as solutions may be poisonois

38
Q

how do you fill the pipette?

A

draw the solution above the graduation mark and run out until the bottom of the meniscus reaches the zero mark, read at eye level

39
Q

how is the solution transferred from a pipette? why?

A

by touching the tip off the inside of the flask, this ensures the exact volume is transferred

40
Q

do you blow the last drop out of the pipette? why?

A

no, it is accounted for in the calibration of the pipette

41
Q

what is the function of the narrow neck on the conical flask?

A

prevents spillage during swirling

42
Q

what is the function of the conical flask in a titration?

A

this is the vessel in which the two solutions will react

43
Q

what do you wash the conical flask with and why?

A

only deionised water as not to change the number of moles of solute taking part in the reaction

44
Q

how accurate does the burette measure?

A

to 0.1 cm cubed accuracy

45
Q

how is the burette clamped and why?

A

clamped vertically to avoid the error of parallax

46
Q

where does the acid USUALLY go?

A

the burette

47
Q

where does the base USUALLY go?

A

the pipette

48
Q

what do you wash the burette with before the titration and why?

A

deionised water and then the solution it will contain. water droplets would dilute the solution

49
Q

how do you fill the burette

A

close tap, add a funnel, fill above zero graduation mark, remove funnel, add a waste beaker underneath. read at eye level, open tap until the bottom of the meniscus reaches the zero graduation mark.

50
Q

one liquid that is read from the top of the meniscus in the burette and why

A

KMnO4 because of its deep purple colour

Chemistry (Tara) (50 decks)

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