Question

A tiny pencil mark just visible to the naked eye contains about 3 × 1017 atoms of carbon. what is the mass of this pencil mark in grams?

Answer 1

The number of carbon atoms in the pencil mark is 3X1017 atoms of carbon The atomic weight of carbon is 12.01 amu, so 12.01 g of carbon contains 6.022X1023 atoms. Thus equation: 12.01 g carbon/ 6.022 X 1023 atoms (3X1017 atoms) (12.01 g carbon/ 6.022X1023 atoms) - the atoms cancel out (3X1017) (12.01g carbon/6.022X1023) divide and multiply = 6x10-6g carbon The mass of this pencil mark in grams is 6x10-6g carbon