Researching Chemistry: Stoichiometric Calculations

Section 1: Understanding Stoichiometry

Stoichiometry is the section of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction.
This involves mathematical calculations to find how much of a reactant is required, or how much product is produced in a chemical reaction.
A stoichiometric equation is balanced when both sides of the equation have equal numbers of each type of atom.
The stoichiometric coefficients refer to the numbers in front of reactants and products in the balanced chemical equation. They represent the molar ratios of the reactants and products.

Section 2: Stoichiometric Calculations

Stoichiometric calculations use the relationship between reactants and products in a chemical reaction.
Avogadro’s number (6.022 x 10^23) is used to compare the number of particles, such as atoms, ions, or molecules, in a substance.
The molar mass is the weight of one mole of a substance. It is calculated using the atomic masses of its components.
To calculate the number of moles from given mass, we use the formula: Number of moles = mass ÷ molar mass.

Section 3: Limiting Reactants and Excess

The reactant that gets completely consumed in a reaction is the limiting reactant, as it limits the amount of product formed.
Reactants that are not completely used up are in excess.
The limiting reactant can be identified by comparing the amount of product each reactant would produce and determining which produces the least amount of product.

Section 4: Theoretical, Actual and Percentage Yield

Theoretical Yield is the maximum amount of product that can be produced from a given amount of reactant.
Actual Yield is the amount of product actually produced from a reaction, which is usually less than the theoretical yield due to factors like side reactions, loss during transfer, etc.
Percentage Yield is the actual yield expressed as a percentage of the theoretical yield. It is calculated by (Actual Yield ÷ Theoretical Yield) × 100.

Section 5: Reaction Stoichiometry in Solutions

When calculating stoichiometry in solutions, the concentration of a solution is an important factor. It is the amount of solute in a given volume of solution, usually expressed as moles per litre (mol/L) or Molarity (M).
Dilution of solutions is described by the formula C1V1 = C2V2, where C and V refer to the concentrations and volumes of the initial and final solutions, respectively.

Section 6: Energy Changes in Stoichiometric Calculations

Every chemical reaction involves an energy change. This can be an exothermic reaction that releases energy, or an endothermic reaction that absorbs energy.
The energy change in a chemical reaction is reported in kJ/mol, which is the amount of energy change per mole of reactants or products. It is calculated from the bond energies of the reactants and products.
These energy changes are central to many chemical processes, including industry processes, energy generation, and biochemistry reactions.