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Titration is a method used in chemistry to determine the concentration of a solute in a solution. In this process, a solution of known concentration, called the titrant, is added to a solution with an unknown concentration until the reaction reaches its endpoint. This point often involves a noticeable change, such as a color shift, indicating the completion of the chemical reaction. In the given exercise, silver nitrate ( AgNO_3 ) acts as the titrant, and it is carefully added to a potassium bromide ( KBr ) solution.
The endpoint in this method is determined using the Mohr titration, where a visible color change marks the completion of the reaction. However, the process involves performing a blank titration to account for any impurities or reactions that do not involve the analyte. This step is crucial to ensure accuracy, and the volume used in the blank titration must be subtracted from the total to find the net volume of silver nitrate needed to react with the potassium bromide.
Thus, titration provides a reliable way to measure an unknown concentration by referencing the stoichiometry of the reaction involved in the method. By carefully measuring the volume of the titrant and using the known concentration, you can deduce the number of moles of each reactant participating in the chemical reaction.

Mole calculations play a central role in understanding chemical quantities in reactions. They allow us to convert between mass, moles, and number of molecules using the concept of the mole, which is a standard unit in chemistry. In the exercise, mole calculations are crucial to determine how much KBr is in the sample.
Initially, the volume of AgNO_3 used in the titration is converted into moles using its molarity: \( \text{moles} = M \times V \), where \( M \) stands for molarity, and \( V \) is the volume in liters. The reaction between AgNO_3 and KBr involves a 1:1 mole ratio, meaning one mole of AgNO_3 reacts with one mole of KBr.
By calculating the moles of AgNO_3 used, you directly determine the moles of KBr, as they are equal at the endpoint of this titration. This involves multiplication with the molar mass of KBr to find the mass of KBr in the original sample. Understanding this stoichiometric relationship helps deduce the quantity of substance involved in the chemical process.

Weight percentage (% w/w) is a common way to express concentrations in chemical mixtures and solutions. It quantifies how much part of a substance makes up the whole in terms of weight. In simpler terms, it tells you the proportion of a particular component within a mixture based on weight.
In this example, the weight percentage of KBr is calculated using the formula: \( \% \text{w/w} = \left( \frac{\text{mass of KBr}}{\text{mass of sample}} \right) \times 100 \% \). This percentage indicates how much of the sample's weight is due to KBr, providing insight into its concentration.
Using the calculated mass of KBr in the sample, and the total mass of the original sample, the weight percentage is calculated to be 43.8\%. This helps chemists and engineers to determine the purity of materials, evaluate their properties, or assess their suitability for specific applications. Expressing concentration in weight percentage is particularly useful when the total weight of the sample or batch is more important than the volume.