1.2: Amount Of Substance Flashcards

(15 cards)

1
Q

What is the equation for %yield?

A

Actual / theoretical x100

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2
Q

What is the formula for atom economy?

A

Mr desired product / Mr total reactants x100

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3
Q

What is the ideal gas equation?

A

PV=nRT
Where ,
P= pressure (Pa)
V= volume (m3)
N= amount of a gas (moles)
R= gas constant (8.31 J/K)
T= temperature (K)- C+273

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4
Q

How could you check that all the water has been removed from a hydrous substance

A

Reheat to a constant mass

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5
Q

What conditions in the fermentation of glucose to ethanol can cause the production of ethanoic acid as a biproduct?

A

Aerobic conditions, air gets in causing oxidation.

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6
Q

What is ‘an appropriate number of significant figures’?

A

The minimum number of significant figures in the question

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7
Q

What are the two universal indications used in titrations?
What are their colour changes?

A
  • phenolphthalein: alkali=pink, acid=colourless
  • methyl orange: alkali=yellow, acid=colourless
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8
Q

Why are only a few drops of universal indicator used in titrations?

A

Too much, the indicators colour masks the colour/colour change were looking for

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9
Q

What must concordant results be within?

A
  • 0.01cm^3
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10
Q

How do you calculate mean titre?

A
  • mean of concordant results
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11
Q

What is the genral titration equation?

A
  • acid + alkali —> salt + water
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12
Q

What is the biuret uncertainty and therefore the total uncertainty?

A
  • +/- 0.05
  • 0.1
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13
Q

What are the genral steps of a titration calculation

A
  • write equation
  • calculate moles of known solution
  • molar ratio
  • calculate moles unknown solution
  • calculate mass with Mr
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14
Q

What are back titrations?

A
  • excess of an acid or alkali is reacted with a substance of unknown mass of substance
  • remove left over acid/alkali and titrate it with an alkali/acid
  • find volume and therefore moles of acid in excess
  • multiply moles up to volume(if changed, e.g only 25cm^3 of a 250cm^3 solution is titrated)
  • use molar ratio to find moles of substance
  • find mass
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15
Q

What are the general steps of a back titration?

A
  • find moles of titration, use molar ratio to find moles of excess
  • fix volume
  • molar ratio with unknown substance
  • find moles and mass
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