Question

Arrange the following in order of increasing mass? 16 water molecules 2 atoms of lead 0.0000000000000051 moles of helium

Answer 1

A clever unit conversion problem!

Consider,

`16"molecules" * ("mol")/(6.02*10^23"molecules") * (18g)/"mol" approx 4.8*10^-22g`

of water,

`2"atoms" * ("mol")/(6.02*10^23"atoms") * (207.2g)/"mol" approx 6.8*10^-22g`

of lead, and (this is why we use scientific notation, sheesh!),

`5.1*10^-15"mol" * (2g)/"mol" approx 1.0*10^-14g`

of helium.

Hence,

`"He" > "Pb" > H_2O` in terms of mass.

This proves just how many molecules are in a mole. Thank God, they don't sell eggs in that quantity.