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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ReplyDeletestill don't get it
ReplyDeletemeant to put it as a reply rather than a comment, but see below. I hope it helps
Deletemass of A + mass of B = mass of AB (as a compound).
ReplyDeletemass 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.
Does anyone know a site for the new GCSE syllabus 2019?
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