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a level chemistry > module 2: moles and calculations > Flashcards

module 2: moles and calculations Flashcards

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1
Q

why is the theoretical yield of an experiment not achieved

A
  1. incomplete reaction
  2. side reactions may have taken place
  3. purifying the product could lead to some of the product being lost
  4. reversible reactions as the products can react with each other and form the reactants
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2
Q

why may percentage yield be over 100

A
  1. some water is left unevaporated
  2. impurities were formed
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3
Q

what is atom economy

A

it’s a measure of how well atoms have been utilised

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4
Q

how do you get a 100% atom economy?

A

use a reaction that only forms one product

find uses for the ‘waste’ products

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5
Q

what are isotopes

A

atoms of the same element that have the same numbers of protons and electrons but different numbers of neutrons

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6
Q

what is the mass number

A

the sum of protons and neutrons in an atom

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7
Q

what is the atomic number

A

the number of protons in an atom

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8
Q

what is meant by relative isotopic mass

A

it’s the mass of an isotope compared with 1/12 mass of a carbon-12 atom

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9
Q

what is meant by relative atomic mass

A

it’s the weighted mean mass of an atom compared with 1/12th mass of a carbon-12 atom

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10
Q

what equation links molecules, moles and Avagadrogo’s number

A

molecule = moles x Avagadro

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11
Q

what equation is used to calculate atomic mass based on isotopes

A

atomic mass based on isotopes = (isotope 1 x abundance 1) + (isotope 2 x abundance 2) / 100

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12
Q

what equation links the no. of moles and volume
(dm³)

A

no. of moles = volume (dm³) / 24

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13
Q

what equation links the no. of moles and volume
(cm³)

A

no. of moles = volume (cm³) / 24000

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14
Q

what is the conversion from cm³ to dm³ and vice versa

A

cm³ to dm³ = divide by 1000
dm³ to cm³ = multiply by 1000

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15
Q

what equation links concentration and volume and moles

A

moles = concentration (moldm-³) x volume (dm³)

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16
Q

what equation links volume, mass and concentration

A

mass = concentration (gdm-³) x volume (dm³)

17
Q

how do you convert from gdm-³ to molsdm-³ and vice versa

A

gdm-³ to molsdm-³ = divide by Mr
molsdm-³ to gdm-³ = multiply by Mr

18
Q

how do you calculate percentage yield

A

percentage yield = actual yield / theoretical yield x 100

19
Q

how do you calculate atom economy

A

atom economy = Mr of desired product / Mr of all products x 100

20
Q

what is an advantage of a high atom economy

A

less natural resources are used, meaning less waste

21
Q

what is the ideal gas equation (with units)

A

pV=nRT
p = pressure, Pa
V = volume, m³
n = number of moles
R = the gas constant (8.31Jk^-1mol^-1)
T = temperature (K)

22
Q

when is the ideal gas equation used

A

under conditions than 298K/25˚C and 1 atm pressure (10^5Pa) where volume of 1 mol of gas is 24dm³, the ideal gas equation must be used

23
Q

define empirical formula

A

The simplest whole number ratio of atoms (of each element) present in a compound

24
Q

what is the Celsius to kelvin conversion

A

celsius + 273

25
Q

what are standard conditions

A

25˚C
1atm
1moldm^-3

26
Q

order
dm³, cm³ and m³

A

smallest to largest
cm³
dm³
m³

27
Q

how many grams are in a tonne

A

1,000,000

28
Q

what is a salt

A

when the H+ of an acid is replaced with a metal/positive/ammonium ion

29
Q

why is it important to develop sustainable reactions

A

low atom economies mean lots of waste is produced and it’s expensive to separate and dispose of the waste products safely

reactant chemicals are usually expensive and money is wasted if there are lots of waste products produced

low atom economies are less sustainable because they use up raw materials that are already in limited supply

reactions that can run at lower temperatures and pressure are cheaper and better to run for the environment

30
Q

how would rinsing the burette with deionised water affect the titre

A

it wouldn’t, because the deionised water doesn’t react with the acid or change the number of moles of it

31
Q

what even is Mr

A

the mass of 1 mol of a thing
molar mass!!!! durrrr

32
Q

examples of weak acids

A

any carboxylic acids

33
Q

examples of strong acids

A

not carboxylic acids
eg. hydrochloric, sulfuric, nitric

34
Q

examples of strong bases

A

have OH in them

35
Q

examples of weak bases

A

don’t have OH in them

36
Q

outline the mechanism of hydroxynitrile formation

A
37
Q

why is ice larger and less dense than water

A

Hydrogen bonds hold the water molecules further apart when frozen vs liquid and the bonds become rigid when frozen vs being constantly broken and reformed in water

a level chemistry (15 decks)

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