Question

A 1.000-g sample of lead shot reacted with oxygen to give 1.077 g of product. Calculate the empirical formula of the lead oxide

Answer 1

 The empirical  formula  of  lead oxide  is  PbO

  Calculation

Step  1:  find the  mass  of  oxygen that reacted

  =mass of the product- mass  of lead

= 1.077 g - 1.000 =0.077 g

Step 2:  find  the mole of each reactant

 moles = mass/molar mass

the molar mass of Pb  =207 g/mol  while that of O = 16g/mol from periodic table

moles of lead(Pb)  is therefore = 1.000 g / 207 g/mol =0.0048  moles

  moles of O2  =0.077g/16 g/mol =0.0048 moles

Step  3:  find the mole  ratio

that is divide each mole by smallest number of mole (0.0048)

Pb = 0.0048/0.0048 =1

O=0.0048/0.0048 =1

• from  mole ratio  above in 1 atom  of Pb of the product we have  1 atom of O  therefore  the empirical formula is PbO