Chemistry practice problems

Introduction
Practice quizzes
Sample tests
Homework
Self-help worksheets for selected introductory chemistry topics
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Introduction

I write problem sets, worksheets, tutorials at various times. In each case, there is some original context that makes the particular document "relevant". Then, things change, and I accumulate stuff. This page lists a range of things, all of which loosely are sets of practice problems, with some limited instructional material included in some cases.

This page may be useful for people just browsing the web site looking for some practice. Students in my current courses can access all problem sets from this page, but note that more complete information focused on the course may be available from the course page.

Those who are using my web site materials for self-study... You are welcome -- and encouraged -- to ask me questions when difficulties arise. (My contact information is at the bottom of each of my web pages.) It always helps if you include how you would answer the question and why. That lets me respond to what you are thinking, lets me focus my reply on where you are having trouble. Further, it gives me a feel for the level at which you are addressing the question -- which may vary depending on your background and course level. The level of discourse -- and your learning of the subject matter -- is enhanced by trying to focus on reasons, not simply answers.

What is the difference between the various kinds of materials listed here, in the various sections? For each section, there is some general descriptive material. However, I suggest visitors look at materials of different types, and decide what is suitable for their situation. A "quiz" can be used as a "worksheet", if that suits you -- or vice versa; both have problems to work and explanatory material, just in different arrangements.

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Practice quizzes

Introductory Chemistry (X11)    Introductory Organic and Biochemistry (X402)

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Sample tests

These are actual tests from previous classes. They are posted here with answer keys.

Introductory Chemistry (X11)    Introductory Organic and Biochemistry (X402)   

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Homework

Most of the homework for the chem classes is from the book. However, in some cases, I provide small additional sets to supplement particular areas. Unless noted, these are distributed with the appropriate chapter handouts, and are also available here as PDF files. They include answers.

Introductory Chemistry (X11)
* Stoichiometry. A small extra set with several questions, of a range of complexity, on a single reaction. The emphasis is that balanced equations give you the mole ratios between the chemicals in the reaction.
* Solutions: weight percentage and dilution. A few extra questions on a couple of topics where the book set is very limited. The dilution problems aim you to use the logical two-step method for calculating dilutions, as I show it in class.

Introductory Organic and Biochemistry (X402)
* Combustion. Writing balanced equations for combustion of organic compounds. This is for the "alkanes" chapter of the org/bio course, but may also be useful for students in general chemistry.
* Aromatic substitution reactions. This set focuses on simple, one-step reactions. It is for the "aromatics" chapter of the org/bio course.
* Name these chemicals (web page). A challenging exercise, based on an ad from a chemical company. It is best suited for late in the course, when students have learned about most of the functional groups.

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Self-help worksheets for selected introductory chemistry topics

The items listed below are self-help handouts; most are available as Microsoft Word DOC files or the RTF or PDF files made from them. Some of these were originally written for a self-paced course in which a variety of chemical calculations were covered through such handouts. The general approach is that basic knowledge of the topic is assumed (that is, these are intended for review and practice), the main issues are presented briefly, and there are lots of practice problems.

For information on how to download or read files, see page File problems. That page also discusses file formats.

Please let me know if you have trouble accessing any files; sometimes, your comment is the way I find out that there is a problem.

Dimensional Analysis    Density    Exploring the chemistry of the earth's crust (elements, periodic table)    Formulas of ionic compounds    Naming chemicals    Mass-mole interconversions    Solutions: Molarity    Solutions: Percentage    Solutions: Dilutions    pH; water    Strong acids    Weak acids    Buffers   

Dimensional Analysis. Download diman.pdf.

Table of Contents for diman.pdf:
A. Introduction
B. Simple unit conversions; the idea of dimensional analysis
C. Multi-step conversions
D. Velocity and density as conversion factors
E. Answers
Download "Dimensional Analysis" (diman.pdf)

Density. Download density.pdf.

Table of Contents for density.pdf:
A. Introduction
B. Calculate d
C. Calculate m
D. Calculate V
E. Misc problems
F. More complexity?
G. Answers
Download "Density" (density.pdf)

Exploring the chemistry of the earth's crust

Practice dealing with elements and the periodic table. The worksheet gives you some data about the abundances of the elements in the earth's crust, and asks some exploratory questions.

The question set, with graph (on back of page), is handed out in class. You can get the files, and an answer sheet, here:
The question set is Crust worksheet: Exploring the chemistry of the earth's crust.
The graph, and the table from which it is derived, are in the accompanying Crust Excel spreadsheet.
Answer sheet.

Formulas of ionic compounds. Download ionic.pdf.

To figure out the formula of an ionic compound you need to 1) identify the ions, then 2) create a neutral compound from those ions. This handout focuses on the second step. The main conceptual issue is that ionic compounds are neutral. To help you focus on that second step, the ions are given in all exercises here. Some of the practice is with imaginary ions, so you are not distracted by trying to figure out what the ions are.

Naming chemicals.

This worksheet deals with naming of simple inorganic compounds, either ionic compounds or covalent compounds of two non-metals. To determine the name of a chemical you must first decide which type of chemical of it. This worksheet guides you to first classify the chemicals, then name them.

This worksheet is available both as a web page and as a pdf file. In either case, the answers are on the web page.
* Web page: Naming chemicals. Includes an expanded introduction and answers with explanations.
* pdf file: Naming chemicals handout. The original class handout, with a brief introduction and the questions. Use the web site, just above, for answers and explanations.

Mass-mole interconversions. Download gmol.pdf.

Table of Contents for gmol.pdf:
A. Introduction
B. Mass-mole interconversions: simple
C. Mass-mole interconversions: complex
D. Answers
Download "Mass-mole interconversions" (gmol.pdf)

Solutions: Molarity. Download molar.pdf.

Table of Contents for molar.pdf:
A. Introduction
B. Molarity
C. Making "molar" solutions
D. Using "molar" solutions
E. Other mole-based concentration units [optional]
F. Answers
Download "Solutions: Molarity" (molar.pdf)

Solutions: Percentage. Download wtpc.pdf.

Table of Contents for wtpc.pdf:
A. Introduction
B. Comparisons; ratios; the idea of percentage
C. The units of "percent"
D. Weight percentage, %(w/w)
E. Volume percentage, %(v/v)
F. Weight/volume percentage, %(w/v)
G. ppm, etc.
H. Converting from w/w to w/v
I. The approximation of dilute aqueous solutions
J. Converting from w/w or w/v to moles or molarity
K. More Problems
L. Answers
Download "Solutions: Percentage" (wtpc.pdf)

Solutions: Dilutions. Download dil.pdf.

Table of Contents for dil.pdf:
A. Dilutions: Introduction
B. The dilution equation
C. The logic of the dilution equation
D. Should you "memorize" the dilution equation? -- Attention X11 students
E. Practical notes
F. Dilutions involving other concentration units
G. Problems
H. Dilution factor
I. Multiple dilutions; serial dilutions
J. Answers
Download "Solutions: Dilutions" (dil.pdf)

pH; water. Download water.pdf.

Table of Contents for water.pdf:
A. Introduction
B. Water
C. [H+] and [OH-] can vary...
D. ... but not independently
E. pH
F. pThis and pThat [optional]
G. Answers
Download "pH; water" (water.pdf)

Strong acids. Download acidstr.pdf.

Table of Contents for acidstr.pdf:
A. Introduction
B. Strong acids: an example
C. Strong acids: general
D. Strong bases
E. More problems
F. What if you have both? [optional]
G. Normality [optional]
H. Answers
Download "Strong acids" (acidstr.pdf)

Weak acids. Download acidwk.pdf.

Table of Contents for acidwk.pdf:
A. Introduction
B. Weak acids: overview
C. Weak acids: an example; finding Ka
D. Given Ka, calculate pH
E. A variety of weak acids
F. So where do strong acids fit in this picture?
G. More problems and questions
H. Polyprotic acids [briefly noted]
I. Sulfuric acid [briefly noted]
J. Weak bases [briefly noted]
K. Answers
Download "Weak acids" (acidwk.pdf)

Buffers. Download buffer.pdf.

Table of Contents for buffer.pdf:
A. Introduction
B. Overview
C. Reversing reversible reactions
D. The acetic acid equilibrium: quantitative re-examination
E. Generalizing... The Henderson-Hasselbalch equation
F. Choosing a buffer
G. Some misconceptions
H. Answers
I. Table of buffers
Download "Buffers" (buffer.pdf)


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Other chemistry materials are available on the Download page.

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Last update: January 07, 2014