Potassium bromide \(\mathrm{KBr}\) contains \(32.9 \%\) by mass potassium. If \(6.40 \mathrm{~g}\) of bromine reacts with \(3.60 \mathrm{~g}\) of potassium, calculate the number of moles of potassium which combine with bromine to form \(\mathrm{KBr}\).

Stoichiometry is the section of chemistry that relates to the quantitative relationships and calculations based on the law of conservation of mass in chemical reactions. It essentially tells us exactly how much of each substance is needed to react completely with other substances in a chemical reaction. This calculation is vital for creating desired chemical compounds in the correct proportions.

In the exercise provided, stoichiometry is used to determine how much potassium bromide (KBr) can be formed from a given amount of potassium. In stoichiometry, it is important to understand the molar proportion of the reactants and products. In simpler terms, stoichiometry helps us answer the question: 'How much of reactant A is needed to react with reactant B to create C products?'

The mole concept is a fundamental principle in chemistry that provides a bridge between the atomic world and the macroscopic world we can measure. One mole of any substance contains Avogadro's number of entities (atoms, molecules, ions, electrons, or other particles), which is approximately 6.022 x 10^23.

In the context of the exercise, understanding the mole concept is crucial for converting the mass of an element (in grams) into moles, as moles are the units used in chemical equations to represent the number of particles involved in the reaction. For instance, when given the mass of potassium, the exercise requires you to calculate the number of moles of potassium, which can be achieved using the formula: \( \text{number of moles} = \frac{\text{mass}}{\text{molar mass}} \).

Chemical reactions are processes where substances, known as reactants, transform into new substances, known as products. This transformation occurs through the breaking and forming of chemical bonds. Each reaction is governed by specific stoichiometry, which defines the amounts of reactants and products involved.

In the exercise, you're analyzing the chemical reaction in which potassium (K) reacts with bromine (Br) to form potassium bromide (KBr). It is essential to understand that during the chemical reaction, the mass and atoms are conserved, which means they are merely rearranged from reactants to form the products, hence linking back to the concept of stoichiometry.