How do you use a balanced equation to calculate reacting masses?

You use a balanced equation to calculate reacting masses by applying the law of conservation of mass and stoichiometry.

In a balanced chemical equation, the numbers in front of the chemical formulas (coefficients) represent the number of moles of each substance. These coefficients can be used to calculate the mass of reactants and products in a chemical reaction. This is based on the law of conservation of mass, which states that the total mass of the reactants is equal to the total mass of the products.

To calculate the reacting masses, you first need to balance the equation. This ensures that the number of atoms of each element is the same on both sides of the equation. Once the equation is balanced, you can use the coefficients to determine the ratio of moles of each substance involved in the reaction. This is known as the stoichiometric ratio.

Next, you need to convert these mole ratios into mass ratios. This is done by multiplying the number of moles by the molar mass of each substance. The molar mass is the mass of one mole of a substance, and can be found on the periodic table.

For example, consider the reaction between hydrogen and oxygen to form water: 2H2 + O2 → 2H2O. The balanced equation tells us that two moles of hydrogen react with one mole of oxygen to produce two moles of water. The molar mass of hydrogen is 1 g/mol, and that of oxygen is 16 g/mol. Therefore, 4 g of hydrogen react with 32 g of oxygen to produce 36 g of water.

Remember, it's important to always check your calculations and ensure that the total mass of the reactants equals the total mass of the products, as per the law of conservation of mass.