Final answer:
To determine the grams of oxygen required for various chemical reactions, one must consider the stoichiometry of the reaction, which is the ratio of reactants to products. Using the balanced chemical equations, along with the molar mass of oxygen, allows for the calculation of the necessary mass or volume of oxygen gas.
Step-by-step explanation:
Understanding Oxygen in Chemical Reactions
When assessing the amount of oxygen needed for a chemical reaction, it is essential to consider the stoichiometry of the reaction. The stoichiometry denotes the ratio of reactants to products in a balanced chemical equation. For instance, the combustion of octane, C8H18, is described by the balanced chemical equation:
C8H18 + 25/2 O2 → 8 CO2 + 9 H2O
To balance the equation, we consider the number of atoms of each element in the reactants and products. In the provided examples, you can see how coefficients are used to balance oxygen in these equations. Calculating the mass of oxygen gas (O2) needed for these reactions involves using the molar mass of oxygen (32.00 g/mol) to convert moles to grams.
For example, to find out the volume of oxygen required for the combustion of ethylene, C2H4, under standard conditions, you will use the ideal gas law and the stoichiometry of the balanced equation:
C2H4 (g) + 3 O2 (g) → 2 CO2 (g) + 2 H2O (g)
The balanced chemical equation shows that for every mole of ethylene, three moles of oxygen are required. Similarly, to calculate the mass of oxygen gas needed to react with a certain amount of a substance, such as magnesium, you use the balanced chemical equation for magnesium combustion:
2 Mg + O2 → 2 MgO
In all these cases, the stoichiometry of the reaction dictates the quantity of oxygen needed for the reaction to occur fully.