A student titrates an unknown amount of potassium hydrogen phthalate \(\left(\mathrm{KHC}_{8} \mathrm{H}_{4} \mathrm{O}_{4}\right.\), often abbreviated \(\mathrm{KHP}\) ) with \(20.46 \mathrm{~mL}\) of a \(0.1000 M\) NaOH solution. KHP (molar mass \(=204.22\) \(\mathrm{g} / \mathrm{mol}\) ) has one acidic hydrogen. What mass of KHP was titrated (reacted completely) by the sodium hydroxide solution?

Stoichiometry is a fundamental concept in chemistry that involves the quantitative relationships between the reactants and products in a chemical reaction. It is based on the conservation of mass and the law of definite proportions. The key to solving any stoichiometric problem is to first write down the balanced chemical equation for the reaction. From this equation, you can determine the mole ratio of the reactants and products involved.

In the case of an acid-base titration like the one in the exercise, stoichiometry tells us how many moles of the titrant (in this case, sodium hydroxide, NaOH) are needed to react completely with a specific amount of the titrand (potassium hydrogen phthalate, KHP). A balanced chemical equation reveals that the reaction between KHP and NaOH occurs in a 1:1 molar ratio, where one mole of KHP reacts with one mole of NaOH to produce the products. When performing an actual titration, the endpoint is reached when this exact stoichiometric proportion is achieved, indicating that the amount of titrant added is stoichiometrically equivalent to the amount of substance in the sample.

The molar mass of a compound is the mass in grams of one mole of that compound. It is a vital concept in stoichiometry as it provides a bridge between the mass of a substance and the number of moles, allowing chemists to quantify substances based on their mass. The molar mass is obtained by summing up the atomic masses of all the atoms in a molecule, as reported on the periodic table of elements, and it is expressed in grams per mole (g/mol).

To calculate the mass of any substance involved in a chemical reaction, you would multiply the number of moles of the substance by its molar mass. In our textbook problem, the molar mass of KHP is given as 204.22 g/mol. By knowing the moles of KHP that reacted, we can determine its mass by using the formula: Mass = Moles × Molar Mass. This step is crucial as it translates the abstract concept of 'moles' into a tangible mass that can be measured in a laboratory setting.

A chemical reaction is a process where substances, known as reactants, undergo a chemical change to form new substances, called products. This process involves the making and breaking of chemical bonds and can result in various physical changes such as color change, temperature change, and the formation of precipitates or gas.

Each chemical reaction is represented by a chemical equation that must be balanced to obey the law of conservation of mass. This means the number of atoms of each element in the reactants must equal the number of atoms of that same element in the products. The balanced equation provides us with the stoichiometric coefficients that describe the ratio in which the compounds participate in the reaction. In the context of an acid-base titration, the reaction between the acid (KHP) and the base (NaOH) produces a salt (NaKP) and water (H2O). By understanding the specifics of the chemical reactions involved, students can grasp why certain products are formed and predict the outcomes of similar reactions.