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A mole is a measure of the amount of substance. One mole contains 6 x 1023 (also known as
the Avogadro Number) particles (atoms, molecules or formulae) of the substance. For example,
1 mol of sodium contains 6 x 1023…

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Mg + S MgS means 1 mole of magnesium will react with 1 mole of sulphur to form
one mole of magnesium sulphide.

What does this mean? It means that 2 moles of magnesium will react to 2 moles of sulphur to
form 2 moles of…

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4g of calcium = 0.1mol of calcium
1 mole of calcium will react to give 1 mole of calcium oxide so
1.1 moles of calcium will give 0.1 moles of calcium oxide

The question asks for the mass of calcium oxide formed so:

Calculate the RFM…

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Work out the RFM of CaCO3 to convert the given mass into moles:

CaCO3 = 40 + 12 + 3(16) = 100g
Number of moles of 30g of CaCO3 = 30/100 = 0.3 mol

By now you should know how to interpret chemical equations in terms…

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The concentration of our hydrochloric acid solution is 2 mol dm-3. This means 1000cm3 of this
bottle of HCl solution contains 2 moles of HCl. We only need one mole so:

(1 mol/2mol) x 1000cm3 = 500cm3 (we can do it the easier way by simply…

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The question says that 40 cm3 of HCl neutralized the sodium hydroxide. This means that 40 cm3
of HCl solution contains 0.005 moles of HCl. All we need to do is use this information and put it
in the form X mol dm-3 :

0.005/40 =…



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