Question

A light alloy consist of 70% of aluminium and 30% magnesium bye mass what would you expect is density to be density of aluminium 2700 kg per metre cube and that magnesium 1740 kg per metre cube

Answer 1

Answer:

On way of working this type of problem is to assume that one starts with an alloy mass of 1 kg = 1000 g.

Then there would be 0.70 x 1000 = 700 g oif Al and .30 x 1000 = 300 g Mg.

Since the Molar Mass of Al is 26.982 g /mole , there are 700/ 26.982 = 25.94 molles of Al, similarly there are

300 / 24.303 = 12.34 moles of Mg (Molar mass of Mg is 24.305)

Thus the mole fraction of Al ( f Al ) is 25.94/(25.94 + 12.34) = 0.6776

and the mole fraction of Mg (f Mg ) is 12.34 /(25.98 + 12.34) = 0.3224

The density of alloy will then be 0.6776 x 2700 + 0.3324 x 1740 = 2390 kg / m^3