Question

activity 1 – atoms, molecules, moles, and mass – 10 points
purpose
to explore the mole concept and practice conversions using molar mass and avogadro’s number.
task
answer the following questions using the vocabulary of unit 2. complete all calculations by showing your
work and reporting answer with correct units and correct significant figures. submit your handwritten
work on this document or on a separate sheet of paper and submit electronically as a pdf to the activity 2
assignment folder.
the mole and molar mass

1. how many atoms of copper (cu) are in a group of 187 dozen copper atoms?

1. how many atoms of copper (cu) are in a group of 187 moles of copper atoms?

1. how many water molecules are in a group of 255 moles water molecules?

1. given the formula for water is h₂o, how many hydrogen atoms are in a group of 255 moles water

molecules?

1. what contains more atoms: 1 mole of sodium atoms or 1 mole of calcium atoms?

Explanation:

Step1: Convert dozen to atoms

Since 1 dozen = 12 items, multiply the number of dozen by 12.
$187 \times 12 = 2244$

Step2: Convert moles to Cu atoms

Use Avogadro's number ($6.022 \times 10^{23}$ atoms/mol), multiply moles by the constant.
$187 \times 6.022 \times 10^{23} = 1.126114 \times 10^{26}$

Step3: Convert moles to water molecules

Multiply moles of water by Avogadro's number.
$255 \times 6.022 \times 10^{23} = 1.53561 \times 10^{26}$

Step4: Find H atoms in water

1 mole $\text{H}_2\text{O}$ has 2 moles H atoms. First find total H moles, then multiply by Avogadro's number.
Total H moles: $255 \times 2 = 510$
H atoms: $510 \times 6.022 \times 10^{23} = 3.07122 \times 10^{26}$

Step5: Compare moles of atoms

1 mole of any element contains Avogadro's number of atoms.
1 mol Na = $6.022 \times 10^{23}$ atoms; 1 mol Ca = $6.022 \times 10^{23}$ atoms

Answer:

1. 2244 copper atoms
2. $1.13 \times 10^{26}$ copper atoms (rounded to 3 significant figures)
3. $1.54 \times 10^{26}$ water molecules (rounded to 3 significant figures)
4. $3.07 \times 10^{26}$ hydrogen atoms (rounded to 3 significant figures)
5. 1 mole of sodium atoms and 1 mole of calcium atoms contain the same number of atoms.