question: What is added to a measured portion of a more concentrated stock solution to achieve a particular concentration?
distractor3: pigment
distractor1: water
distractor2: yeast
correct_answer: solvent
support: Dilution is also a common means of preparing solutions of a desired concentration. By adding solvent to a measured portion of a more concentrated stock solution, we can achieve a particular concentration. For example, commercial pesticides are typically sold as solutions in which the active ingredients are far more concentrated than is appropriate for their application. Before they can be used on crops, the pesticides must be diluted. This is also a very common practice for the preparation of a number of common laboratory reagents (Figure 3.17).