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calculations - Coggle Diagram
calculations
calculations linking moles, Ar and Mr
One mole of any element is equal to the relative atomic mass of that element in grams or for a compound the relative formula mass in grams
To find the mass of one mole of a compound, we add up the relative atomic masses
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reacting masses
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Then, the ratio between the substances is identified using the balanced chemical equation
Once the moles have been determined they can then be converted into grams using the relative atomic or relative formula masses
MgO combustion practical
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Measure mass of crucible with lid. Add sample of magnesium into crucible and measure mass Strongly heat the crucible for several minutes. Lift the lid frequently to allow air into the crucible for the magnesium to fully oxidise without letting magnesium oxide smoke escape. Continue heating until the mass of crucible remains constant, Measure the mass of crucible and contents
empirical formula
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divide each of the two masses by the relative atomic masses of the elements and simplify the ratio. Represent the ratio into the form ‘MxOy‘ E.g, MgO
CuO reduction practical
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Place metal oxide into a horizontal boiling tube and measure the mass. Support the tube in a horizontal position and pass over a steady stream of methane and burn off the excess gas. Heat the copper (II)oxide strongly until metal oxide changes colour (all O2 removed) Measure mass of the tube remaining metal powder
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the mole
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The number of atoms, molecules or ions in a mole (1 mol) of a given substance is the Avogadro constant. The value of the Avogadro constant is 6.02 x 1023 per mole
relative formula mass
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To calculate the Mr of a substance, you have to add up the relative atomic masses of all the atoms present in the formula
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percentage yield
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The theoretical yield is the amount of product that would be obtained under perfect practical and chemical conditions, calculated from reacting masses
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In practice, you never get 100% yield in a chemical process for several reasons
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