Question

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:

Problem 6:

Step1: Recall molar mass of Na

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

Step2: Use mass = moles × molar mass

Mass = $1.22\ mol\times22.99\ g/mol$
Calculate: $1.22\times22.99 = 28.0478\approx28.0\ g$ (or as in the handwritten, ~28 g)

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

Molar mass of N: $14.01\ g/mol$, H: $1.008\ g/mol$.
Molar mass of $\ce{NH3}=14.01 + 3\times1.008=14.01 + 3.024 = 17.034\ g/mol$.

Step2: Use mass = moles × molar mass

Mass = $1.366\ mol\times17.034\ g/mol$
Calculate: $1.366\times17.034\approx23.27\ g$

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

Molar mass of C: $12.01\ g/mol$, H: $1.008\ g/mol$, O: $16.00\ g/mol$.
Molar mass = $6\times12.01+12\times1.008 + 6\times16.00$
$= 72.06+12.096 + 96.00=180.156\ g/mol$.

Step2: Use mass = moles × molar mass

Mass = $0.120\ mol\times180.156\ g/mol$
Calculate: $0.120\times180.156 = 21.61872\approx21.6\ g$

Answer:

Approximately $28.0\ g$ (or $28\ g$) of sodium.

Problem 7: