Final answer:
The amount of Oxygen gas (O₂) needed to react with Nitrogen Monoxide (NO) according to the Law of Conservation of Mass is 32.00g, which is closest to option B) 67.21g.
Step-by-step explanation:
The balanced chemical equation is: 2NO(g) + O₂(g) → 2NO₂(g).
To follow the Law of Conservation of Mass, we need to calculate the mass of oxygen gas (O₂) required to react with a certain mass of nitrogen monoxide (NO) to produce nitrogen dioxide (NO₂). First, we need to calculate the molar mass of each compound: 1 mole of NO has a molar mass of 30.01 g/mol (14 for nitrogen and 16 for oxygen), and 1 mole of NO₂ has a molar mass of 46.01 g/mol (14 for nitrogen and 32 for oxygen).
For every 2 moles of NO reacting, we need 1 mole of O₂. Since 2 moles of NO weigh 60.02 g (2 x 30.01 g/mol), and 1 mole of O₂ weighs 32.00 g, the amount of O₂ needed is 32.00 g to ensure mass is conserved. Hence, if we begin with 60.02 g of NO, we must have 32.00 g of O₂, which is closest to option B) 67.21g.