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Once you got the moles of water and anhydrous salt, you can determine the empirical formula drom finding the ratio of these two substances in the hydrate by making the number of moles into whole numbers. Take the same steps as part A to deter mine the number of moles of anhydrous salt.
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In order to determine the empirical formula, you need to know the moles of anhydrous salt present in hydrate. Number of moles of water = mass of water x 1 mole water / 18.0g waterī: Determining the empirical formula of the hydrate. Since you know the mass of water, it is easy to determine the moles of water present in hydrate! ( See the previous post for steps to calculate the moles of substance in a compound!)
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% water = mass of water / mass of hydrate x 100 ( For calculating percent composition of a compound, see the previous post! ) Since you know the mass of hydrate and water, you can calculate the percent composition of the water. Simply, when you take the mass of the hydrate before heating and subtract the mass of the hydrate after heating (which is anhydrous salt ), that's the mass of water given off by the hydrate. To determine the percentages of water, you need to know the mass of water given off by the hydrate. Add a few drops of water to the comtents of the crusible and note any changes occured.Ī: Determining the percentages and moles of the water. Reheat the crusible with hydrate to make sure that all the water is driven off.ĥ. Turn off the burner,let it cool, and determine & record the mass of it.Ĥ. Heat the crusible with hydrate in it for about 5 min. Place the hydrate into the crusible, determine & record the mass.ģ. The formula for water is set apart at the end of the formula with a dot, followed by a coefficient that represents the number of water molecules per formula unit. Sodium hydroxide is used in many industries, mostly as a strong chemical base. The name of the compound is cobalt (II) chloride hexahydrate and its formula is CoCl 2 6H 2 O. One liter of the solution contains 572g of NaOH. It is used in titration and to increase alkalinity, to neutralize acids and to make sodium salts. Heat the crusible to make sure that it is dry. After cooling the crusible, determine & record the mass of the empty crusible.Ģ. Sodium Hydroxide Solution, 40 Weight, Chem-Lab is a strong base and is highly caustic. Set up the equipments ( crusible, pipestem triangle, iron ring, & bunsen burner) as shown on the right. Also, we added a few drops of water to the remainings to see how the colour of hydrate have changed.ġ. Basicly, all we did was to heat the unknown hydrate and weight the remaining hydrate to see how much water was given off by the hydrate. Today, we had a lab on determining the percentage and moles of water in an unknown hydrate and writing the empirical formula of the hydrate. A hydrate is an ionic compound that has a definite amount of water molecules attached to its crystalline structure.