INTRODUCTION: Most substances which we encounter in our everyday lives are not pure compounds or elements but mixtures of these. We encounter mixtures all the time. One group of mixtures is called homogenous mixtures or solutions. The air we breathe is a gaseous solution. The water we drink and swim in is an aqueous solution. Metals that we use in our lives are typically solutions of different metals, called alloys. Solutions are made of two components, solvent and solute. Water is the most common solvent. In fact, water is called the universal solvent because so many different types of substances dissolve in it. Gases, salts, organic molecules all dissolve in water. Since it is a liquid these solutes are free to move around and are easily transported from one place to another. Water solutions are also one of the most common environments for chemical reactions. Of course water is essential for our lives and when scientists seek for life on other planets one of the first things they look for is evidence of water. In this unit we will consider different types of solutions and then focus on aqueous solutions. We will learn how to measure the components in a solution. Our lab activities will give us an opportunity to make solutions and determine the concentration of ions in a solution. Lastly, we will also examine some salt solutes with regard to their solubility in water.
OBJECTIVES: As you study this unit, you should be able to do the following:
Distinguish between solvent and solute in a solution. (15.2)
Explain why all soluble ionic compounds are electrolytes. (15.2)
Differentiate among saturated, unsaturated, and supersaturated solutions. (16.1)
Explain how solutions form, define solubility and describe the factors that affect solubility. (16.1)
Describe the factors that affect the rate at which a solute dissolves in a substance. (16.1)
Measure and calculate the concentration of a solution in terms of molarity, and apply calculations to stoichiometry problems involving solutions. (16.2 and GIAs)
As a class generate a Beer’s Law Graph comparing absorbance to concentration of a dissolved substance and use this graph to estimate the concentration of an unknown substance. (Lab activity)
Define a colligative property of a solution and describe three such properties. (16.3)
Define chemical equilibrium and explain how it is achieved in relation to reversible reactions. (18.2)
Write the equilibrium constant, Keq, expression from a balanced chemical equation. (18.2)
Analyze the extent of the reaction or position of the equilibrium based upon the size of the equilibrium constant, Keq. (18.2)
Explain Le Chatelier’s Principle and describe how changes in concentration, pressure and temperature affect a reaction at equilibrium. (18.2)
Write the Ksp expression for a dissolution/precipitation equilibrium and calculate the equilibrium ion concentrations for a slightly soluble salts. (18.3)
Predict whether or not a precipitate will form when two solutions are mixed, based on a solubility table or the table of general solubility rules for ionic compounds. (18.3)
LEARNING ACTIVITIES:
To learn about objectives 1-8:
READ Chapter 15, pp. pp. 445-458 and Chapter 16, pp. 470-490. See objectives for specific section. [N.B. We are skipping the section on “Calculations Involving Colligative Properties” on pp. 491-197, and the mathematical relationships used to calculate colligative properties.]
Complete “Chem Activity 33: Molarity” as a group of four in class.
READ Lab “Making Solutions and Measuring Their Concentrations.”
PERFORM and WRITE Lab according to instructions on the sheet.
Complete GIA 8-2: Solution Stoichiometry.
ANSWER and SOLVE appropriate questions and problems on
the Self-Test.
To learn about objectives 9-14:
To make sure you understand the objectives for this unit:
ASK me, the teacher, any lingering QUESTIONS
COMPLETE the Unit’s Self-Test and Check your answers.
Due Dates:
Quiz on Ch.16: (Objectives 1-8) Day 4 of week of March 31, 2008
Ch. 16 questions: due same day as the quiz.
Ch. 18 questions: same day as test on Unit 8.
Test on Unit 8:
