Mass, Calculations + Analysis
- Created by: chickpeatweet
- Created on: 23-04-14 10:57
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- Mass, Calculations + Analysis
- Mass of Atoms
- Relative mass of protons + neutrons is 1
- Atomic number = number of protons
- same as number of electrons
- Mass number = protons + neutrons in nucleus
- Isotopes version of same element with different number of neutrons
- Masses of Atoms and Moles
- Atoms too small to weigh
- use relative atomic mass
- Average value for isotopes of an element
- Ar
- use relative atomic mass
- Relative formula mass = all the relative atomic masses added up in a compound
- eg. The Mr of CaCl2
- Ar of Ca = 40
- Mr = 111
- Ar of Cl x 2 = 71
- Mr = 111
- Ar of Ca = 40
- Mr
- eg. The Mr of CaCl2
- Atoms too small to weigh
- Percentages and Formulae
- Relative atomic mass of element in compound used to wok out percentage composition
- eg. Percentage of carbon in CO2
- Ar of C = 12
- Mr = 44
- Percentage = (12 / 44)x100
- 27.3%
- Percentage = (12 / 44)x100
- Mr = 44
- Ar o O x 2 = 32
- Mr = 44
- Percentage = (12 / 44)x100
- 27.3%
- Percentage = (12 / 44)x100
- Mr = 44
- Ar of C = 12
- eg. Percentage of carbon in CO2
- Emperical formula is the symbol of the compound, ie. CH3 or CaCl2
- Work out with given masses or percentage composition
- eg. Emperical formula of hydrocarbon that contains 80% carbon
- Mass in 100 grams
- Carbon = 80
- Hydrogen = 20
- Divide mass by Ar
- 80/12 = 6.67
- 20/1 = 20
- Divide by smallest number
- 6.67/6.67 = 1
- 20/6.67 = 3
- Emperical formula =
- CH3
- Mass in 100 grams
- Relative atomic mass of element in compound used to wok out percentage composition
- Yield
- Tells you how much is made
- The percentage yield tells you the max amount that could be made
- calculated before reaction takes place
- percentage yield =
- amount of product / max amount
- maximum amount is calculated from the balanced equation
- amount of product / max amount
- In industry, high percentage yield needed
- Reduce waste and pollution
- Gas Chromatography - C2
- Analysing a substance for addiitves or food colouring
- mass spectrometry
- Mass of Atoms
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