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Description
Mind Map by amelia.peterson, updated more than 1 year ago
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Created by amelia.peterson
about 11 years ago
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Chemistry C2.3
- The Mass of Atoms
- Relative mass of protons and neutrons = 1
- Mass number = protons + neutrons
- Number of protons and electrons are always the same
- Number of protons and electrons are always the same
- Mass number = protons + neutrons
- Isotopes - atoms of the same element with different number of neutrons
- Mass number is the top number
- Relative mass of protons and neutrons = 1
- Masses of Atoms and Moles
- Relative atomic mass (Ar)is used to compare atom masses
- Relative atomic mass = mass number
- Relative formula (Mr) = mass numbers added together
- Relative formula (Mr) = mass numbers added together
- Relative formula mass in grams is call one mole of that susbstance
- NaOH = 23 + 16 + 1 = 40 1 mole of NaOH = 40g
- Relative atomic mass (Ar)is used to compare atom masses
- Percentage and Formulae
- Percentage = relative atomic mass / relative formula mass x100
- % of carbon in CO2 = 12 + 16 +16 = 44 12/44 x100 = 27.3%
- Empirical Formula - simplest ratio of atoms/ions in a compound
- Divide mass of each element by its Ar and convert to simplest ratio
- Formula of hydrocarbon that contains 80% carbon:
Carbon = 80/12 = 6.67 Hydrogen = 20/1 = 20
6.67/6.67 = 1 20/6.67 = 3 Formula = CH3
- Formula of hydrocarbon that contains 80% carbon:
Carbon = 80/12 = 6.67 Hydrogen = 20/1 = 20
6.67/6.67 = 1 20/6.67 = 3 Formula = CH3
- Divide mass of each element by its Ar and convert to simplest ratio
- Percentage = relative atomic mass / relative formula mass x100
- Equations and Calculations
- Balanced symbol equations show how many moles of a substance are used e.g. 2Mg + 02 = 2 moles of Mg and 1 O
- 24 + 24 + 16 = 80g
- 24 + 24 + 16 = 80g
- 1g of Mg = 80/48 MgO 5g of Mg = 80/48 x 5 = 8.33g
- You can work in moles or relative masses for calculations
- Balanced symbol equations show how many moles of a substance are used e.g. 2Mg + 02 = 2 moles of Mg and 1 O
- Instrumental Analysis
- Modern instrumental methods - quick, accurate, sensitive BUT expensive need training to use
- Samples need to be separated for compounds to be identified - gas chromatography linked to mass spectrometer
- Comounds are split as travel at different speeds
- Comounds are split as travel at different speeds
- Mass spectrometer gives the relative molecular mass from its ion peak
- Modern instrumental methods - quick, accurate, sensitive BUT expensive need training to use
- The Yield of a Chemical Reaction
- Yield - how much product you actually make
- Percentage yield - amount of product collected / maximum amount of product possible x 100
- 48g of Mg should give 80g of MgO so 2g of Mg should give 80/48 x 2 = 3.33 MgO
Percentage Yield = 2.3/3.33 x 100 = 69%
- High yields conserve resources and reduce waste - should waste little energy - reduce pollution
- Yield - how much product you actually make
- Reversible Reactions
- Can only occur if products of a reaction can react to make the original reactants
- Reversible reactions represented by double arrow
- Ammonium chloride can be heated, reactants formed cool to react and form ammonium chloride
- Can only occur if products of a reaction can react to make the original reactants
- Analysing Substances
- Food additives - to improve its qualities, can be natural or synthetic
- Chemical analysis used to check safe additives have been used in food
- Paper chromatography, mass spectrometry - methods
- Paper chromatography, mass spectrometry - methods
- Paper chromatography - analyse artificial colours in food
- Colours move different distances depending on their solubility
- Colours move different distances depending on their solubility
- Food additives - to improve its qualities, can be natural or synthetic
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