Lesson Plan Solubility and Solubility Product Constant

Topics: Solubility, Solubility equilibrium, Sodium chloride Pages: 5 (1194 words) Published: September 25, 2011
School : Senior High School
Topic: Solubility product of Constant (Ksp)
Grade : XI
Semester : 2
Time Allocated: 30 minutes

I. Competency Standard
Understanding properties, measuring method and applying of acid base solutions.

II. Basic Competency
Predicting precipitation from a reaction based on solubility and solubility product constant principle

III. Indicator
1. Explain the meaning of Solubility Product Constant (Ksp) 2. Write down the Solubility Product Constant’s Formula

Learning Objectives
Cognitive and psychomotor
Students are able to:
1. Identify anions and cations presence in the solution with precipitation based on the value of solubility product constant (Ksp) 2. Predicting relative solubility of some salts based on the value of solubility product constant (Ksp) 3. Write down the solubility product constant’s formula 4. Predicting precipitation from a reaction based on the value of solubility product constant (Ksp) 5. Communicate the observations result

1. Student active answer the questions

IV. Learning Materials
3. Prerequisite concept
Solubility is the amount of solute that dissolves in a given quantity of a particular solvent at a given temperature to give a saturated solution. Neutralisation
When an alkali is added to an acid, the pH of the mixture rises as the alkali reacts with it forming neutral products. An acid added to an alkali causes the pH to fall because the alkali is removed by reaction with the acid. A reaction in which acidity or alkalinity is removed is called neutralisation. A neutralisation involving an acid and a base (or alkali) always produces salt and water (and nothing else). Acid + base salt + water

4. Main Concept
Salts differ in their solubilities. In general, compounds of alkali metals are soluble in water. Many ionic compounds however, are insoluble. Most “ insoluble” salts will dissolve to some extent in water. These salts are said to be slightly soluble in water. For example, when the “insoluble” salt AgCl is mixed with water, a very small amount of it dissolves. Molar solubility of ionic compounds

It is convenient to define the solubility of ionic substances in units of g per 1000 g of saturated solution, or as the number of moles of substance needed to produce 1 dm3 of saturated solution. Molar solubility is defined as follows: The molar solubility of a compound is its concentration (mol dm3) in a saturated solution at that temperature.

Molar solubility is given the symbol s. Ionic compounds which are only slightly soluble in water are said to be sparingly soluble. Examples include silver chloride (Ag+, Cl-) and barium sulfate (Ba2+,SO42-). Since such compounds are only slightly soluble, the volume of water used to dissolve a salt may be taken to be equal to the volume of the solution. (For example, if we dissolve 0.0010 g of silver chloride in 1000 cm3of water, we may safely assume that the volume of the solution is also 1000 cm3.) This approximation does not hold for very soluble salts, where the presence of appreciable concentrations of salt in the water causes a slight change in the liquid volume. One reminder – although many ionic substances are only sparingly soluble in water, any ionic substance thatdoes dissolve completely dissociates into separate ions. Solubility product of sparingly soluble salts

Experiments show that, for a saturated solution of silver chloride, [Ag+(aq)]x [Cl(aq)] = a constant at that temperature
Where the square brackets signify equilibrium concentrations in mol dm3. This is the solubility product expression for silver chloride. The constant is known as the solubility product or solubility constant (symbolized Ks) for AgCl(s) at that temperature. At 25oC, Ks(AgCl)= 1.6x10-10 mol2dm-6, i.e. [Ag+(aq)] x [Cl (aq)] = Ks(AgCl) = 1.6x10-10mol2dm-6

We can put this into words as follows: ‘In a solution...
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