CHEMISTRY · Multi-part · CBSE · Chemistry · Acids, Bases and Salts · Acids, Bases and Salts
Problem
Copper(II) sulfate pentahydrate, CuSO4⋅5H2O, is commonly used as a drying agent in organic synthesis. In preparing a laboratory stock, a chemist isolates a portion that contains exactly 2.50×1022 water molecules bound within the crystalline hydrate. Assume the formula unit CuSO4⋅5H2O is strictly obeyed throughout the sample. Avogadro’s constant is 6.022×1023mol−1.
(a) Calculate the number of moles of water molecules present in the sample.
(b) Using the stoichiometric relationship inherent in the hydrate formula, determine the number of moles of CuSO4⋅5H2O present.
(c) Compute the mass of the hydrate sample in milligrams. Report your answer with three significant figures.
(d) Using your results from parts (a)–(c), determine the percent by mass of water in this sample and compare it with the theoretical percent by mass of water in pure CuSO4⋅5H2O. Explain any difference or lack thereof.