Barium hydroxide product constant

We saw in Section 8.5 that an enthalpy change is often called a heat of reaction because it is a measure of the heat flow into or out of a system at constant pressure. If the products have more enthalpy than the reactants, then heat has flowed into the system from the surroundings and AH has a positive sign. Such reactions are said to be endothermic (endo means "within," so heat flows in). The reaction of 1 mol of barium hydroxide octahydrate with ammonium chloride, for example, absorbs 80.3 kj from the surroundings (AH° = +80.3 kj). The surroundings, having lost heat, become so cold that water freezes around the outside of the container (Figure 8.6). 

Pour, in a thin stream, with constant stirring, the hydrogen peroxide solution into the barium hydroxide solution in the 2-liter bottle. Let the flaky barium peroxide hydrate settle and then collect it on a suction filter. As soon as the water is drawn out, shut off the suction, wash with 15 cc. cold water, press the solid into a compact cake, and again suck dry. Do not draw any quantity of air through the product. Wrap the crystals in paper towels and dry them according to Note 9 (6), page 15. Preserve the product in a 4-ounce cork-stoppered bottle. 

The equilibrium of a solvation reaction has its own equilibrium constant called the solubility product Ksp. Use Ksp the same way you would use any other equilibrium constant. Remember that solids and pure liquids have an approximate mole fraction of one and can be excluded from the equilibrium expression. Thus, solids are left out of the solubility product expression as in the example of the Ksp for barium hydroxide shown below. 

To the solution of barium hydroxide (275 g) in distilled water (500 ml), MDP (83 ml) was added over a period of 30 min with constant stirring. The reaction was carried for more than 3 h, while the temperature was maintained below 30 C. After the completion of the reaction, the reaction mixture was acidified with Cone. HCl till the pH of the solution was reduced to 2.0. The compound OC -chloroacrylic acid was then extracted with several portions of a solution containing 1 g of hydroquinone for every 200 ml of diethyl-ether. The ether extract was then dried over anhydrous magnesium sulfate overnight. The product was then isolated by evaporating the ether under reduced pressure. The crude product was recrystallized from hexane at low temperature to get 60 g of -chloroacrylic acid (MP 64-65°C). 

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