Question 20 a raindrop has a mass of 50. mg and the pacific ocean has a mass of * 7.081020kg. use this information to answer the questions below. be sure your answers have the correct number of significant digits.

The questions you can answer are

1) what is the mass of one mole of raindrops?, and

2) How many moles of raindrops are in the pacific ocean

Solutions:

1) what is the mass of one mole of raindrops?

mass = number of rain drops * mass of on rain drop

The number of rain drops in one mole of rain drops is 6.02 * 10^23

So, the mass of one mole of rain drops is

6.02 * 10 ^ 23 rain drops * 50. mg * (1 kg / 1,000,000 mg) = 3.01 * 10^ 19 kg

The correct number of significant digits is 2, because 50. mg has two signficant digits, so the answer must be shown as 3.0 * 10^ 19 kg.

2) How many moles of raindrops are in the pacific ocean

Use the proportion 1 mol / 3.0 * 10^19 kg = x mol / 7.08 * 10^20 kg

And you solve for x:

x = (7.08 * 10^20 kg) * 1 mol / (3.0 * 10^19 kg) = 2.36 * 10 = 23.6 moles

Which rounded to two significant digits is 24 moles of rain drops.