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# Stoichiometry

AP.Chem: SPQ‑4 (EU), SPQ‑4.A (LO), SPQ‑4.A.1 (EK), SPQ‑4.A.2 (EK), SPQ‑4.A.3 (EK)

## Problem

$\ce{K2CO3}(aq) + \ce{CaCl2}(aq) \rightarrow \ce{2KCl}(aq) + \ce{CaCO3}(s)$
A student conducts an experiment to determine the molarity of a $\ce{K2CO3}(aq)$ solution of unknown concentration. The student mixes 100, point, start text, m, L, end text of the solution with excess $\ce{CaCl2}(aq)$, causing $\ce{CaCO3}(s)$ to precipitate. The student then filters and dries the precipitate and records the data in the table below. (The molar mass of $\ce{CaCO3}$ is 100, point, start text, g, slash, m, o, l, end text.)
Mass of filter paper0, point, 70, space, g
Mass of filter paper + $\ce{CaCO3}$ precipitate1, point, 95, space, g
What is the molarity of the $\ce{K2CO3}(aq)$ solution?