Question

how many grams of o₂ are required to produce 358.5 grams of zno?
2zn+o₂ → 2zno
70.4 g
14.5 g
29.1 g
1300 g

Explanation:

Step1: Calculate molar mass of ZnO and O₂

Molar mass of Zn: \(65.38\space g/mol\), O: \(16.00\space g/mol\).
Molar mass of \(ZnO = 65.38 + 16.00 = 81.38\space g/mol\).
Molar mass of \(O_2 = 2\times16.00 = 32.00\space g/mol\).

Step2: Find moles of ZnO

Moles of \(ZnO = \frac{mass}{molar\space mass} = \frac{358.5\space g}{81.38\space g/mol} \approx 4.405\space mol\).

Step3: Relate moles of ZnO to O₂ (from balanced equation)

From \(2Zn + O_2
ightarrow 2ZnO\), 2 moles of ZnO are produced from 1 mole of \(O_2\).
Moles of \(O_2 = \frac{1}{2} \times\) moles of \(ZnO = \frac{1}{2} \times 4.405\space mol \approx 2.2025\space mol\).

Step4: Calculate mass of O₂

Mass of \(O_2 = moles \times molar\space mass = 2.2025\space mol \times 32.00\space g/mol \approx 70.48\space g\) (close to 70.4 g).

Answer:

70.4 g