The Law of Conservation of Mass: A Fundamental Principle in Chemistry
How does the Law of Conservation of Mass apply to a chemical reaction?
The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction, only rearranged. This means that the total mass of the reactants must equal the total mass of the products. Given this principle, how can we determine the combined mass of the products formed in a specific chemical reaction?
Answer:
The combined mass of the products formed in a chemical reaction can be calculated by considering the stoichiometry of the reaction and the molar masses of the substances involved. Let's take a closer look at this concept using the following example:
When a 3.43-gram silicon dioxide sample reacts with 2.17 grams of solid carbon, the products formed are silicon carbide and carbon monoxide gas. The balanced chemical equation for this reaction is: SiO2 + 3C -> SiC + 2CO.
To determine the combined mass of silicon carbide and carbon monoxide gas that should be formed, we first need to calculate the moles of silicon dioxide and solid carbon. Silicon dioxide has a molar mass of 60.08 g/mol, so the moles of SiO2 is 3.43 g / 60.08 g/mol = 0.057 mol. Solid carbon has a molar mass of 12.01 g/mol, so the moles of solid carbon are 2.17 g / 12.01 g/mol = 0.18 mol.
According to the balanced chemical equation, 1 mole of silicon dioxide produces 1 mole of silicon carbide and 2 moles of carbon monoxide. Therefore, the moles of silicon carbide formed is 0.057 mol x 1 mol / 1 mol = 0.057 mol, and the moles of carbon monoxide formed is 0.057 mol x 2 mol / 1 mol = 0.114 mol.
To find the combined mass of silicon carbide and carbon monoxide gas, we calculate the mass of silicon carbide (0.057 mol x 40.10 g/mol = 2.29 g) and the mass of carbon monoxide gas (0.114 mol x 28.01 g/mol = 3.20 g). Adding these masses together gives a combined mass of 2.29 g + 3.20 g = 5.49 grams.
Thus, the combined mass of silicon carbide and carbon monoxide gas that should be formed in this reaction is 5.49 grams, in accordance with the Law of Conservation of Mass.