Question

unit 7 - moles
calculate the number of moles in each of the following masses

1. how many grams are in 1.22 moles of sodium?
2. how many grams are in 1.366 mol of nh₃?
3. how many grams are in 0.120 mole of glucose, c₆h₁₂o₆?
4. how many grams are in 6.94 moles of barium chloride, bacl₂?
5. how many grams are in 0.05 mol of propane, c₃h₈?

Explanation:

Question 6

Step1: Recall molar mass of Na

Molar mass of Na is $22.99\ \text{g/mol}$.

Step2: Use mass = moles × molar mass

Mass = $1.22\ \text{mol} × 22.99\ \text{g/mol}$
Calculate: $1.22×22.99 ≈ 28.05\ \text{g}$

Step1: Calculate molar mass of $\ce{NH3}$

Molar mass of N: $14.01\ \text{g/mol}$, H: $1.008\ \text{g/mol}$.
Molar mass of $\ce{NH3}$ = $14.01 + 3×1.008 = 17.034\ \text{g/mol}$.

Step2: Use mass = moles × molar mass

Mass = $1.366\ \text{mol} × 17.034\ \text{g/mol}$
Calculate: $1.366×17.034 ≈ 23.27\ \text{g}$

Step1: Calculate molar mass of $\ce{C6H12O6}$

C: $12.01\ \text{g/mol}$, H: $1.008\ \text{g/mol}$, O: $16.00\ \text{g/mol}$.
Molar mass = $6×12.01 + 12×1.008 + 6×16.00$
= $72.06 + 12.096 + 96.00 = 180.156\ \text{g/mol}$.

Step2: Use mass = moles × molar mass

Mass = $0.120\ \text{mol} × 180.156\ \text{g/mol}$
Calculate: $0.120×180.156 = 21.61872\ \text{g}$

Answer:

Approximately $28.1\ \text{g}$ (or $28.05\ \text{g}$)

Question 7