Stoichimetry

Chapter 4: 1-3 Homework

Reading Preparation
WebLecture
Study Activity
Preparation work for chat
Online Quiz
Lab Instructions

Reading Preparation

Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 4 Sections 1 to 3.

Study Notes

4.1 Stoichiometry — Mass Relationships in Chemical Reactions. This is the nuts and bolts of chemistry. If you have problems understanding this section or any of the examples, be sure that you get them straightened out as soon as possible. We will spend a lot of effort going from molecules to masses and back....because chemists must measure masses and then calculate the number of molecules involved. There is just no easy way to count molecules. Even when it seems overkill, follow the steps outlined here for every problem. When you run into un-obvious problems, the process can help you figure out what you need to know.

4.2 Limiting Reactants. You've already been doing this kind of calculation for the previous section, where you are given one of the reactants' mass or mole level and asked to find out something about the rest of the reaction amounts. Now you want to determine for a particular situation in which you know the amounts of both reactants, which reactant limits the reaction and determines the final amount of the products.

4.3 Percent Yield. According to the laws of entropy, nothing is 100% efficient when it involves the conversion of energy. So chemical reactions rarely go to completion; some of the reactants never react. There are a lot of factors involved (solution concentration, purity of the species, temperature amonght them). The only way to figure actual yield is to do the experiment multiple times. The ratio of actual/perfect is expressed as a percentage. Figuring out ways to increase yield is a large part of the work of industrial chemists.

Moles from Masses	$\frac{mass (grams)}{molar mass (grams)} = moles$
Masses from Moles	$moles * molar mass (\frac{grams}{nol}) = mass$
Percent Yield	$percent yield = \frac{actual yield}{theoretical yield} * 100 %$

Web Lecture

Read the following weblecture before chat: Stoichiometry

Study Activity

Videos for Chapter 4: Chemical Equations

Review the Videos at Thinkwell Video Lessons under STOICHIOMETRY.

The Mole: Introducing Conversions of Masses, Moles and Number of Particles
Solving Problems involving Mass/Mole Relationships: Finding Limiting Reagents
Solving Problems involving Mass/Mole Relationships: Theoretical Yield and Percent Yield.
[LAB related]: Under ATOMS, MOLECULES, and IONS: Atomic Structure - CIA Demonstration: Flame Colors

Use the Reactants, Products, and Leftovers simulation below to gain a better understanding of stoichiometry and limiting reactants.

Use the Sandwiches exercise to build the "target" sandwich in the header. When do you have leftovers? Can you create the right number of sandwiches from your ingredients store so that you don't have leftovers?
Use the "Molecules" exercise to build water molecules, ammonia, and burn methane. Can you balance these reactions?
Take the challenge and see whether you can

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.
Play the game and see whether you can generate the products and leftovers shown for each set of reactions. Can you make it to the expert level 3?

Chapter Quiz

There is no chapter quiz YET.

Lab Work

LAB #1 [Option 2] Solway Process

PHASE I: Create a plan for your lab. This should include your goal, materials, equipment, and procedure. Identify any safety issues in carrying out the procedure, storing your materials, or disposing of them after you complete your lab. Be prepared to discuss your plan in chat.

PHASE II: Carry out the modified Solway decomposition of sodium hydrogen carbonate. If so instructed, combine your data with that of your fellow students for joint analysis of your results.

References (Solway):

IGHCE Lab 9.1 and HSCKM III-1 Observe a Composition Reaction
IGHCE Lab 9.2 and HSCKM III-2 Observe a Decomposition Reaction.

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