In chemistry, knowledge of reactants and products, chemical reactions and types, and solutions and precipitations is vital. These concepts must be studied deeply, qualitatively, and quantitatively. To study a reaction quantitatively, the masses and volumes of reactants and products involved and the percent yields from a reaction are important factors in conducting laboratory investigations and further study of substances. The relationship between the amounts, or quantities, of substances involved in a reaction or compound is described using stoichiometry. The quantitative measure of reactants required to produce useful and practical quantities of products is the foundation for several mass industrial productions of medicines, dyes, fertilizers, pesticides, and other important chemicals. The percent yield of a useful element from extracted raw ore decides whether an extraction of ore through a certain process is beneficial. Understanding how the amounts of substances involved in reactions change, the concepts of molar mass and molar volume, calculations of percent yields, and the reactants that control the yields as limiting reactants is essential to quantitative analysis of chemicals and substances.
At A Glance
- A mole is the amount of substance that has 6.023×1023 particles, and the molar mass is the mass of one mole of a substance.
Mass can be converted to moles by dividing the mass by the molar mass of the substance.
Moles can be converted to mass by multiplying the number of moles of the substance by the molar mass of the substance.
- To find the mass of a product, first convert the mass of the given reactant to moles. Then, use the mole ratio from the balanced chemical equation to convert moles of the reactant to moles of the product. Finally, change the mole of the product to grams.
Moles of a substance are converted to moles of another substance by comparing the mole ratio of a balanced chemical equation.
- The mole ratio from a balanced chemical equation must be used when it is necessary to convert the mass of one substance to the moles of another substance within a chemical reaction.
When products or reactants are gaseous in form at standard temperature and pressure, the molar volume of a gas and mole ratios can be used to convert the volume (in liters) of one substance to moles of another substance. One mole of an ideal gas has a volume of 22.4 L at standard temperature and pressure.
- The theoretical yield of a reaction is the calculated amount of product that is expected to be produced. The amount of the product determined experimentally is the actual yield. The percent yield is the ratio of the actual yield to the theoretical yield, multiplied by 100.
- A limiting reactant is completely used up in a reaction, and other reactants are excess reactants. The amount of product is always calculated based on the number of moles of the limiting reactant.