Question

measuring moles lab
you will visit 8 weighing stations. make note of each of the elements or compounds and the mass. today, your goal will be to calculate the number of moles present in each of the samples. when you take your measurements, each station has an empty container. make sure that you have zeroed the balance with the empty container on the scale before you measure your sample.
compound: carbon
mass of compound: 1304g
molar mass: convert mass to moles:

compound: silicon
mass of compound: 20.45g
molar mass: convert mass to moles:

compound: nacl
mass of compound: 65.43g
molar mass: convert mass to moles:

compound: cacl₂
mass of compound: 30.94g
molar mass: convert mass to moles:

Explanation:

Step1: Find molar mass of Carbon

Molar mass of C = $12.01\ \text{g/mol}$

Step2: Calculate moles of Carbon

$n = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{130.4\ \text{g}}{12.01\ \text{g/mol}} \approx 10.86\ \text{mol}$

Step3: Find molar mass of Silicon

Molar mass of Si = $28.09\ \text{g/mol}$

Step4: Calculate moles of Silicon

$n = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{20.45\ \text{g}}{28.09\ \text{g/mol}} \approx 0.728\ \text{mol}$

Step5: Find molar mass of NaCl

Molar mass of NaCl = $22.99\ \text{g/mol} + 35.45\ \text{g/mol} = 58.44\ \text{g/mol}$

Step6: Calculate moles of NaCl

$n = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{65.43\ \text{g}}{58.44\ \text{g/mol}} \approx 1.120\ \text{mol}$

Step7: Find molar mass of CaCl₂

Molar mass of CaCl₂ = $40.08\ \text{g/mol} + 2\times35.45\ \text{g/mol} = 110.98\ \text{g/mol}$

Step8: Calculate moles of CaCl₂

$n = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{30.94\ \text{g}}{110.98\ \text{g/mol}} \approx 0.279\ \text{mol}$

Answer:

1. Carbon

• Molar Mass: $12.01\ \text{g/mol}$
• Moles: $10.86\ \text{mol}$

1. Silicon

• Molar Mass: $28.09\ \text{g/mol}$
• Moles: $0.728\ \text{mol}$

1. NaCl

• Molar Mass: $58.44\ \text{g/mol}$
• Moles: $1.120\ \text{mol}$

1. CaCl₂

• Molar Mass: $110.98\ \text{g/mol}$
• Moles: $0.279\ \text{mol}$