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1.BASIC CONCEPTS eLearn.Punjab

Example (11):

Calculate the number of grams of K2SO4 and water produced when 14 g of KOH are reacted with
excess of H2SO4. Also calculate the number of molecules of water produced.

Solution:

For doing such calculations, first of all convert the given mass of KOH into moles and then compare

these moles with those of K2SO4 with the help of the balanced chemical equation.

Mass of KOH = 14.0 g
Molar mass of KOH
= 39 + 16 + 1 = 56 g/mol
Number of moles of KOH
= 14.0 g = 0.25
56 g mol-1

Equation: 2KOH(aq) + H2SO4(aq) K2SO4(aq) + 2H2O(l)

To get the number of moles of K2SO4, compare the moles of KOH with those of K2SO4.

KOH : K2SO4
2 : 1

1: 1
0.25 :
2
0.125

So, 0.125 moles of K2SO4 is being produced from 0.25 moles of KOH
Molar mass of K2SO4 = 2 x 39 + 96
= 174 g/mol

Mass of K2SO4 produced = No. of moles x molar mass
= 0.125 moles x 174 g mol-1

=21.75g

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