Homework

Chemical Analysis

Chapter 4: 4-5 Homework

Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 4: Sections 4 and 5.

Study Notes

4.4 Chemical Analysis This section discusses some of the logic and processes chemists use to determine the composition of samples of compounds. Not all methods work in all cases, and experiences is required to chose the best approach. While decomposition methods produce data to help determine the empirical formula, determination of the molecular formula usually requires setting up several different reactions with compounds of known composition, and observing the products.

4.5 Concentrations in Solutions Aqueous solution reactions are affected by the concentration of the solutes and solvents involved. Study the definition of molarity and check the definition of molality as well; know the difference! The two ways of expressing concentration reflect common practices for preparing concentrations in the lab. It is often necessary to prepare solutions of precise molarity for certain chemical reactions, especially those used for analysis or pharmaceuticals. Be able to propose a method of preparation by dilution (this method is the common one, which explains why most chemistry labs have stock solutions of very high —and therefore dangerous — molarities).

Web Lecture

Read the following weblecture before chat: Chemical Analysis: Measuring Concentrations

Videos for Chapter 4: Chemical Equations

Review the Videos at Thinkwell Video Lessons under STOICHIOMETRY and PHYSICAL PROPERTIES OF SOLUTIONS.

• A Problem Using the combined concepts of Stoichiometry
• Characterizing Solutions: Types of Solutions
• Characterizing Solutions: Molarity and the Mole Fraction
• Characterizing Solutions: Molality

Play with the Concentration interactive below and see if you can determine

• How the volume of liquid and the amount of solute are related.
• How the concentration and solution color are related. (How might you use this to determing solution concentration?)
• Can you create a solution of precisely 0.5 mol of any one of the combinations of the available solutes? How?
• How can you change a 0.5 M concentration to a 1.0M concentration precisely?
• How can you change a 1.0 M concentration to a 0.5M concentration precisely?
• When is a solution "saturated? What happens if you add more solute at this point?

Chat Preparation Activities

• Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

Chapter Quiz

• There is no chapter quiz YET.

LAB #2 GUIDED INQUIRY -- Phase II

Carry out your experimental plan and post your data to the website for evaluation and discussion.

References:

• AP2009 14 Separation and qualitative analysis of cations and anions
• APGIE Investigation 9 Physical and Chemical Changes: Can the Individual Components of Quick Ache Relief Be Used to Resolve Consumer Complaints?
• IGHCE Lab 19.1-2 Use Flame Tests and Borax Beads to Discriminate Metal Ions
• IGHCE Lab 19.3 Qualitative Analysis of Inorganic Anions, Cations, and Bone
• (Alternative lab) Flame Tests