If an atom weighs 6.2 × 10^{-4} grams, what is the total weight of a substance which has 5.75 × 10^{10} atoms in the sample? Give the answer in scientific notation to 2 significant figures.
if one atom weighs 6.2 × 10^{-4} grams and we have 5.75 × 10^{10} atoms, to find the total, multiply
= 6.2 × 10^{-4} × 5.75 × 10^{10} = 35|,650,000 since it is 2 significant figures, we need to ‘chop it off’ after the first 2 numbers so the 35 will round to 36 and then put in scientific notation
= 3.6 × 10^{7}