C2 T6 Quantitative Chemistry

Relative Atomic Mass

RAM (Ar) is the same as the MASS NUMBER (top number, usually the bigger number) of any element.

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The sum of all the relative atomic masses added together...
e.g. the Mr of magnesium chloride, MgCl2 would be: Ar of Mg(24) + Ar of Cl (35.5x2) = 95.

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% mass of an element in a compound = [(Ar x no. of element atoms) / Mr of compound] x100%.
e.g. % mass of Na in Na2CO3= 23x2/106 x 100% = 43.4%.

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List the elements in the compound.
Underneath, write down their experimental masses (given in the question).
Divide by the Ar of its element.
Ratio it by multiplying or dividing.
Using the ratio in its simplest form, write the formula of the cmpound.
BASICALLY, DIVIDE THE EXPERIMENTAL MASS BY THE Ar OF THE ELEMENT THEN SIMPLIFY INTO A RATIO TO MAKE A FORMULA FROM.

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Percetage yield compares actual yield and theoretical yield.
% yield = actual yield (g) / theoretical yield (g) x100%
Yield are always less than 100%...
Due to: 1. Incomplete reactions; 2. Practical losses during preparation; 3. Unwanted reactions.
Waste in reactions costs money, so reactions that make lots of waste aren't usually profitable.
Disposing of harmful waste products safely can be very expensive.
Chemists in industry are always looking for ways to produce products in a way that makes the most profit safely.
Chemists work to find reactions with these characteristics:
a) They give a high % yield, so lots of product is made from th expensive raw materials
b) All of the products are comercially useful, depleting waste
c) They are at a suitable speed, so products are made quickly and safely.

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