Question

practice: moles to mass & mass to moles
calculate the mass of each of the following:

1. how many moles are in 64.1 grams of aluminum? al
2. how many moles are 850.5 grams of zinc? zn
3. how many moles are in 3.00 g of boron tribromide, bbr₃?
4. how many moles are in 0.472 g of sodium fluoride, naf?
5. how many moles are in 50.0 g of calcium chlorate, ca(clo₃)₂?

Explanation:

Problem 16:

Step1: Recall molar mass of Al

Molar mass of Al is \( 26.98 \, \text{g/mol} \). The formula to convert mass to moles is \( \text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} \).

Step2: Substitute values

Given mass of Al is \( 64.1 \, \text{g} \). So, moles of Al \( = \frac{64.1 \, \text{g}}{26.98 \, \text{g/mol}} \approx 2.376 \, \text{mol} \).

Step1: Molar mass of Zn

Molar mass of Zn is \( 65.38 \, \text{g/mol} \). Use \( \text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} \).

Step2: Calculate moles

Mass of Zn is \( 850.5 \, \text{g} \). So, moles of Zn \( = \frac{850.5 \, \text{g}}{65.38 \, \text{g/mol}} \approx 12.9 \, \text{mol} \).

Step1: Calculate molar mass of \( \text{BBr}_3 \)

Molar mass of B: \( 10.81 \, \text{g/mol} \), Br: \( 79.90 \, \text{g/mol} \). For \( \text{BBr}_3 \), molar mass \( = 10.81 + 3 \times 79.90 = 10.81 + 239.7 = 250.51 \, \text{g/mol} \).

Step2: Find moles

Mass of \( \text{BBr}_3 \) is \( 3.00 \, \text{g} \). Moles \( = \frac{3.00 \, \text{g}}{250.51 \, \text{g/mol}} \approx 0.0120 \, \text{mol} \).

Answer:

Approximately \( 2.38 \, \text{mol} \) (or \( \frac{64.1}{26.98} \approx 2.376 \), rounded as needed)

Problem 17: