Question

How many moles are there in 78g of pure potssium? [K=39]

Answer 1

Answer:

3.40 g K  contains  5.24 × 10 22  atoms K

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Explanation:

One mole of any element contains  6.022 × 10 23  atoms of that element. The molar mass of an element is the mass in grams of one mole of the element, which is its relative atomic mass (atomic weight) on the periodic table in g/mol.

Potassium,  K , has the relative atomic mass  39.0983 , therefore its molar mass is  39.0983 g/mol

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We need to make the following conversions.

mass K → mol K → atoms K

Divide the given mass by molar mass, then multiply by  

6.022 × 10 23 atoms/mol

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3.40 g K× 1 mol K  39.0983  g K × 6.022 × 10 23  atoms K  

1 mol K  = 5.24  × 10 22 atoms K