Mass of 18.0 mL of water: 18.0 g Mass of 12 marbles: 43.4 g Volume of 12 marbles
ID: 866409 • Letter: M
Question
Mass of 18.0 mL of water: 18.0 g
Mass of 12 marbles: 43.4 g
Volume of 12 marbles: 21.5 mL
Water density: 1.00 g/mL
Marble density: 2.02 g/mL
Questions:
1. What is the number of moles of water present in 18.0 g of water? (use correct sig fig)
2. Use scientific notation for the number of water molecules in 18.0 g of water.
3. How many water molecules would have the mass of one marble?
4. Neglect empty space between molcules and calculate average volume of a water molecule in mL.
5. What is the average volume of a marble?
6. How many water molecules could fit in the same volume as one marble?
Explanation / Answer
1. mass of water = 18g/mol
use the formula nFw = m here n = no. of moles, Fw = formula wt. ex. H2O = 2+ 16 = 18, m = mass given
n = m/Fw = 18g/18g/mol = 1mol
2. 1 mole is equal to 6.023 x 10^23 molecules
As 18g of water has 1 mol of water than it will have 6.023 X 10^23 molecules.
3. For that we have to calculate the mass of a single molecule of water which is
18.0 a.m.u.,
or
18.0 g / 6.023 X 10^23 = 2.99 X 10^-23 grams per each molecule of water
Now mass of 12 marbles = 43.4g
therefore mass of 1 marble = 43.4g/12 = 3.62g
so
3.62g / 2.99 X10^-23 grams = 1.21 X 10^23 molecules of water would have the mass of 1 marble
4. density of water: 1 g/mL
Also 1 mole of water is equal to 18.0 ml
therefore 18.0 ml / 6.023 X 10^23 molecules per mole = 2.99x 10^-23 ml per each molecule of water
Average volume of water molecule = 2.99X 10^-23 per molecule
5. Average volume of a marble
21.5 ml / 12 = 1.79 ml for each marble
6. For No. of water molecules that could fit divide average of a marble by average volume occupied by each water molecule.
1.79 ml marble / (2.99X 10^-23 ml per each molecule of water) = 5.99 X 10^22 molecules