Saturday, 30 March 2013

1.25 calculate reacting masses using experimental data and chemical equations

This means knowing that the mass of A and the mass of B will equal the mass of AB.
Bearing in mind that the mass of one mole of an element is its atomic mass.
If we have 2 moles of A(24) and react it with 5 moles of B(25)
then we have (2x24)+(5x25) and can calculate that A2B5 will weigh 173g

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    1. meant to put it as a reply rather than a comment, but see below. I hope it helps

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  3. mass of A + mass of B = mass of AB (as a compound).

    mass of 1 mole of an element = atomic mass of element.

    So
    mass of 1 mole of A = atomic mass of A
    mass of 1 mole of B = atomic mass of B

    Say A has atomic mass of 24
    and B has atomic mass of 25

    mass of 2 moles of A = 2 x atomic mass
    = (2 x 24)g
    mass of 5 moles of B = 5 x atomic mass
    = (5 x 25)g

    (mass is measured in g, grams)

    2 moles of A + 5 moles of B = A2B5 (the compound contains all 7 moles)

    mass of 2 moles of A + mass of 5 moles of B = mass of A2B5
    (2x24)g + (5x25)g = 173g

    Therefore A2B5 (compound of A and B) has a mass/weight of 173g.

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