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NAME ____________________________ PRELAB FOR HYDRATE LAB FILL IN THE BLANKS IN THE CHART BELOW AND ANSWER THE THREE QUESTIONS. SHOW ALL WORK AND USE SIG DIGS AND UNITS THROUGHOU LAB 5: FORMULA FOR A HYDRATE EXPERIMENT HONORS CHEMISTRY Problem: What is the percentage of water in a hydrated salt? What is the formula for the hydrate? PRELAB: A HYDRATE is a compound that contains water in its crystal structure. The water may be removed from the salt in the laboratory by heating the salt. The salt without the water is called an ANHYDROUS SALT. Here is an example of a hydrate: CoCl2· 6H2O Cobalt(II) chloride hexahydrate hydrate heat anhydrate CoCl2 6H2O(s) --- CoCl2(s) + 6H2O(g) In hydrates, the water molecules are a distinct part of the compound but are joined to the salt by connections that are weaker than the connections in the salt or the connections in the water molecules. Notice, we use a middle dot to connect the water units to the salt formula. NAME OF SALT CoCl2· ?H2O MASS OF CRUCIBLE MASS OF CRUCIBLE & HYDRATED SALT MASS OF HYDRATED SALT 12.090 GRAMS 16.250 GRAMS GRAMS MASS OF CRUCIBLE & CONTENTS AFTER HEATING MASS OF ANHYDROUS SALT 12.424 GRAMS GRAMS MASS OF WATER LOST GRAMS % WATER IN HYDRATED SALT % WATER MOLES WATER IN HYDRATED SALT MOLES FORMULA FOR ANHYDROUS SALT MOLES ANHYDROUS SALT MOLES FORMULA FOR HYDRATED SALT In this experiment you will measure the mass of a hydrated salt, then remove the water from the crystals and measure the mass of the anhydrous salt. The data gathered will allow you to determine the percent water in the hydrated salt and also the EMPIRICAL FORMULA (the simplest whole-number ratio of atoms in a compound) for the hydrated salt. Pre-lab: Complete the table and answer the 3 prelab questions that follow – show your calculations Pre lab questions: 1. What information is necessary to determine the percentage of water in a sample of a hydrate? 2. How will the water be removed from the hydrate in this experiment? 3. A hydrate has the formula of Na3PO4 . 12H2O. What is the percent of water in the hydrate?
