Quantitative Flashcards

1
Q

what is the principle of conservation of mass?

A

no atoms are lost or made during a chemical reaction - mass of products = mass of reactants

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2
Q

what is occurring if there appears to be a mass change in a reaction?

A

reactant or product may be a gas and its mass has not been taken into account e.g. in a reaction of a metal and oxygen or thermal decomposition

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3
Q

how do you calculate % yield?

A

actual yield / theoretical yield * 100

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4
Q

why is % yield never 100%?

A
  • reaction may not go to completion (eg if reaction is reversible)
  • reactants may be impure (may react in different ways)
  • some product lost to equipment when separated from reaction mixture (left behind on apparatus)
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5
Q

define atom economy

A

how much of the total mass of reactants is converted into the desired product

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6
Q

what does a high atom economy mean?

A

less waste - may have high % yield but low atom economy

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7
Q

how do you calculate atom economy?

A

sum of Mr of desired product / sum of Mr of all reactants x 100 (use coefficients to calculate Mr as finding out number of atoms)

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8
Q

how do you calculate relative atomic mass (Ar)?

A

weighted average mass of all isotopes = (mass of isotope 1 x % of I1) + (mass of I2 x % of I2) / 100

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9
Q

how do you calculate relative formula mass (Mr)?

A

sum of relative atomic masses (Ar) in a formula

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10
Q

how do you calculate % composition?

A

(Ar*number of atoms) / Mr * 100

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11
Q

what is a ‘mole’?

A

unit of measurement - 1 mole of any substance contains the same number of the stated particles, atoms, molecules or ions as 1 mole of any other substance

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12
Q

give Avogadro’s constant

A

6.022 x 10^23

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13
Q

what is the mass of 1 mole of a substance in grams numerically equal to?

A

its Ar or Mr

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14
Q

how do you calculate the number of particles?

A

moles x 6.022^23 (x no. atoms)

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15
Q

how do you calculate moles?

A

mass / relative formula mass (N=m/Mr)
concentration * volume (N=cv)
volume of a gas / molar volume (24) (N=v/24)

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16
Q

how do you calculate % uncertainty?

A

uncertainty / vol.measured * 100

17
Q

how do you convert between cm^3 and dm^3?

A

divide by 1000

18
Q

how do you convert between concentration in mol/dm^3 and g/dm^3?

19
Q

what is the molar volume of gas at RTP?

A

24dm^3 or 24,000cm^3

20
Q

what is 1 cubic decimetre in litres?

21
Q

how do you calculate retention factor?

A

distance travelled by substance / distance travelled by solvent

22
Q

how do you calculate to mean rate of a reaction?

A

amount of reactant used / time

23
Q

how do you calculate the mass of an atom in grams?

A

Ar / 6.022 x 10^23

24
Q

how much is 1 tonne in kg?

25
how much is 1kg in g?
1000g
26
how much is 1g in mg?
1000mg
27
how much is 1km in m?
1000m
28
how much is 1m in cm?
100cm
29
how much is 1cm in mm?
10mm
30
How much is 1mm in micrometres?
1000 micrometres
31
how much is 1mm in nm?
1,000,000 nm
32
how much is 1s in ms?
1000ms
33
how much is 1ml in cm^3
1 cm^3