Question

1. calculate the number of atoms in 156.0 grams of gold
2. if you have 3.5 moles of aluminum, how many grams of aluminum do you have?
3. how many atoms are 35.0 grams of calcium?
4. if you have 88.2 grams of lead, how many moles do you have?

Explanation:

Question 13:

Step1: Find moles of gold

Molar mass of gold (Au) is 197.0 g/mol. Moles = mass / molar mass. So moles of Au = \( \frac{156.0\ g}{197.0\ g/mol} \approx 0.7919\ mol \)

Step2: Find number of atoms

Using Avogadro's number (\( 6.022 \times 10^{23}\ atoms/mol \)), number of atoms = moles × Avogadro's number. So atoms = \( 0.7919\ mol \times 6.022 \times 10^{23}\ atoms/mol \approx 4.769 \times 10^{23}\ atoms \)

Step1: Recall molar mass of Al

Molar mass of aluminum (Al) is 26.98 g/mol.

Step2: Calculate mass

Mass = moles × molar mass. So mass = \( 3.5\ mol \times 26.98\ g/mol = 94.43\ g \)

Step1: Find moles of calcium

Molar mass of calcium (Ca) is 40.08 g/mol. Moles = \( \frac{35.0\ g}{40.08\ g/mol} \approx 0.8732\ mol \)

Step2: Find number of atoms

Atoms = moles × Avogadro's number. So atoms = \( 0.8732\ mol \times 6.022 \times 10^{23}\ atoms/mol \approx 5.258 \times 10^{23}\ atoms \)

Answer:

\( \approx 4.77 \times 10^{23}\) atoms (or more precise \( 4.769 \times 10^{23}\))

Question 14: