A Level Chemistry OCR Practice Exam

What does the term standard solution refer to?

1. A solution with unknown concentration

2. A solution made from distilled water

3. A solution of known concentration used in titrations

4. A solution that contains no solute

The correct answer is: A solution of known concentration used in titrations

The term standard solution refers to a solution of known concentration used in titrations. In a laboratory setting, standard solutions are crucial for quantitative analysis as they provide a reliable reference point against which the concentration of an unknown solution can be measured. In titrations, the standard solution is often used to determine the concentration of an analyte in the unknown solution by reacting it to a specific endpoint, which is indicated by a color change or other measurable physical change. This technique relies on the precision of the standard solution's concentration, making it essential for accurate outcomes in various chemical analyses. Other options describe different solutions but do not capture the specific meaning of a standard solution. For instance, a solution with unknown concentration is not classified as a standard solution since its defining characteristic is precisely known concentration. Similarly, while a solution made from distilled water can serve various purposes, it does not inherently define a standard solution, as the key aspect is the concentration, not the purity of the solvent. Lastly, a solution that contains no solute essentially describes a solvent (like pure distilled water), which is not relevant to the idea of a standard solution that has a measurable amount of solute dissolved in it.