Question

question 1. when iron is exposed to air, it corrodes to form red - brown rust. rust is iron(iii) oxide ($fe_2o_3$). how many moles of iron(iii) oxide are contained in 92.2 g of pure $fe_2o_3$?
question 2. how many moles of zinc, zn, are in 0.535 g of zinc?
question 3. how many moles are in 12.15 g of magnesium (mg)?
question 4. find the number of moles in 508 g of ethanol ($c_2h_6o$).

Explanation:

Question 1

Step1: Calculate molar mass of $\text{Fe}_2\text{O}_3$

Molar mass = $2\times55.85 + 3\times16.00 = 159.7\ \text{g/mol}$

Step2: Calculate moles of $\text{Fe}_2\text{O}_3$

$\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{92.2}{159.7}$

Step3: Compute final value

$\text{Moles} \approx 0.577$

Question 2

Step1: Note molar mass of Zn

Molar mass of Zn = $65.38\ \text{g/mol}$

Step2: Calculate moles of Zn

$\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{0.535}{65.38}$

Step3: Compute final value

$\text{Moles} \approx 0.00818$

Question 3

Step1: Note molar mass of Mg

Molar mass of Mg = $24.31\ \text{g/mol}$

Step2: Calculate moles of Mg

$\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{12.15}{24.31}$

Step3: Compute final value

$\text{Moles} \approx 0.4998 \approx 0.500$

Question 4

Step1: Calculate molar mass of $\text{C}_2\text{H}_6\text{O}$

Molar mass = $2\times12.01 + 6\times1.008 + 1\times16.00 = 46.07\ \text{g/mol}$

Step2: Calculate moles of $\text{C}_2\text{H}_6\text{O}$

$\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{508}{46.07}$

Step3: Compute final value

$\text{Moles} \approx 11.0$

Answer:

1. $0.577$ moles
2. $0.00818$ moles
3. $0.500$ moles
4. $11.0$ moles