15.2 Hydrates A compound that contains water of hydration is called a hydrate. In writing the formula of a hydrate, use a dot to connect the formula of the compound and the number of water molecules per formula unit.

Hydrates 15.2 A sample of blue CuSO4·5H2O is heated. Water can be driven from a hydrate by heating. a) Heating of a sample of blue CuSO4·5H2O begins. b) After a time, much of the blue hydrate has been converted to white anhydrous CuSO4.

15.2 Hydrates Blue crystals of CuSO4·5H2O crumble to a white anhydrous powder that has the formula CuSO4. Water can be driven from a hydrate by heating. a) Heating of a sample of blue CuSO4·5H2O begins. b) After a time, much of the blue hydrate has been converted to white anhydrous CuSO4.

15.2 Hydrates When treated paper is exposed to moist air, it turns pink because of the formation of the hydrate cobalt(II) chloride hexahydrate (CoCl2·6H2O). Paper treated with anhydrous cobalt(II) chloride is blue. In the presence of moisture the paper turns pink. Inferring How could you change the pink paper back to blue?

15.2 Hydrates

Hydrates 15.2 Efflorescent Hydrates If a hydrate has a vapor pressure higher than the pressure of water vapor in the air, the hydrate will lose its water of hydration, or effloresce.

Hydrates 15.2 Hygroscopic Hydrates Hydrated salts that have a low vapor pressure remove water from moist air to form higher hydrates. These hydrates and other compounds that remove moisture from air are called hygroscopic.

15.2 Hydrates To determine what percent of a hydrate is water, first determine the mass of the number of moles of water in one mole of hydrate. Then determine the total mass of the hydrate. The percent by mass of water can be calculated using this equation.

15.1 Sample Problem 15.1 15.1

15.1 Sample Problem 15.1

15.1 Sample Problem 15.1

15.1 Sample Problem 15.1

Practice Problem For Sample Problem 15.1 Problem Solving 15.6 Solve Problem 6 with the help of an interactive guided tutorial.

Hydrates 15.2 Deliquescent Compounds Deliquescent compounds remove sufficient water from the air to dissolve completely and form solutions. These compounds become wet when exposed to normally moist air.

15.2 Hydrates The deliquescent substance, sodium hydroxide, absorbs moisture from air. Deliquescent substances can remove water from the air. a) Sodium hydroxide pellets absorb moisture from the air. b) Eventually a solution is formed. Applying Concepts Identify the solvent and the solute.

Hydrates 15.2 A solution forms. Deliquescent substances can remove water from the air. a) Sodium hydroxide pellets absorb moisture from the air. b) Eventually a solution is formed. Applying Concepts Identify the solvent and the solute.

15.2 Section Quiz. 15.2.

15.2 Section Quiz. 1. Choose the correct words for the spaces. In any solution, the material that is dissolved is called the _______ and the material in which the substance is dissolved is called the _______ . solid, liquid solvent, solute solute, solvent crystal, disperser

15.2 Section Quiz. 2. In the solution process, the solvent molecules are surrounded by positive and negative ions. solvent molecules become dispersed in an ionic crystal. ions become emulsified in the solvent. positive and negative ions are surrounded by solvent molecules.

15.2 Section Quiz. 3. All ionic compounds are electrolytes because they conduct electricity in the solid state. dissociate into ions in the aqueous and/or the molten state. remain as positive-negative pairs even when dissolved. only conduct electricity in the molten state.

15.2 Section Quiz. 4. The formula for iron(II) sulfate heptahydrate is FeSO4(H2O)7 FeSO4•(H2O)7 Fe•2SO4•7H2O FeSO4•7H2O

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