How to Calculate Heat When a Substance Is Dissolved in Water
- 1). Weigh the substance on a chemical balance and find its mass in grams.
- 2). Find the chemical's molar mass in the chemical reference manual. Look up the energy of hydration of the chemical. Write these figures down.
- 3). Key the gram mass in the calculator. Divide this by the molar mass. Press the equals (=) key to obtain the number of moles. For example, the molar mass of table salt or sodium chloride is 58.44 grams per mole. If you have 100 grams of salt, 100 divided by 58.44 equals 1.7 moles.
- 4). Multiply the number of moles by the energy of hydration. Press the equals key to see the kilojoules of heat produced when the substance dissolves in water. Using sodium chloride as an example, the heat released is 3.88 kilojoules per mole, and 3.88 x 1.7 = 6.6 kilojoules.
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