A student claims, "If I add an equal volume of water to any aqueous solution, I will…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A student claims, "If I add an equal volume of water to any aqueous solution, I will double the number of moles of solute present." The instructor asks the class to analyze and critique this statement in the context of solution concentration and dilution.
(1) Explain, using the definition of molarity and appropriate reasoning, how adding pure water to a solution affects the concentration of the solute but not the number of moles of solute present.
(2) Assume an initial volume V_i of an aqueous solution has concentration C_i. An equal volume V_i of water is added. Derive an algebraic expression for the new concentration C_f in terms of C_i.
(3) Using your expression from part (b), evaluate C_f when C_i=0.200M. State whether the student’s claim is correct or incorrect and justify your conclusion.
(4) Describe one real-world scenario in which diluting a solution by adding solvent could be hazardous if the change in concentration is misunderstood. Explain the chemical or safety implications involved.