Chemistry 151 competency exam

The purpose of the exam

This competency exam is for students wishing to bypass CH 151 and go straight into CH 221. Students taking this exam must also have successfully completed the following courses: IRW 115 (or Writing 115/Reading 115), and Math 111, or equivalent placement before registering for CH 221.

CH 221: General Chemistry I is the first of a three-term series, 15-credit hour (5 hours/term), chemistry sequence designed to provide a year of general chemistry to science majors. It will meet transfer school requirements for such science majors as chemistry, physics, chemical engineering, pre-medicine, and other pre-professional programs.

To register for CH 221 you must have successfully completed CH 151: Preparatory Chemistry, or you can take this Competency Exam.

Reviewing before you take the exam

The chemistry department has created a list of chemistry and math topics that are covered on the exam. Please see the information below. The chemistry content of the exam is typically covered in Chapters 1-3 in most General Chemistry textbooks. A General Chemistry textbook is on reserve at each PCC campus library.

Study guide

Practice problems for chemistry can be found in the first few chapters of most General Chemistry Textbooks.

Chemistry topics
  • Classify matter and solutions from particle-level pictures and chemical formulas
  • Classify matter as a pure substance, mixture, element, compound, homogeneous, or heterogeneous
  • Distinguish between particles (atoms, molecules, ions) and the categories of matter they compose (element, covalent or ionic compound, mixture)
  • Identify chemical and physical properties and chemical and physical changes
Measurement and problem-solving
  • Significant figures and what they mean
    • Uncertainty in glassware
    • Record measurements with the correct number of significant figures
    • Significant figures in calculations
    • Precision versus accuracy
  • Units of measurement
    • Convert metric to metric or metric to alternate system using dimensional analysis with proper significant figures
    • Know the most common metric conversion factors (i.e. nano, micro, milli, centi, kilo, mega)
    • Complete multiple-step conversions, including steps with exponents (e.g. ft2 to cm2 )
    • Density calculations
Atoms and elements
  • Structure of the atom
    • Compare the mass and volume of the nucleus and the electrons in an atom
    • Determine the number of each subatomic particle (protons, neutrons, and electrons) given a formula of an atom, ion, or isotope
    • Relate the charge of an ion to the number of protons, neutrons, and/or electrons
    • Know the difference between atomic mass, mass number, and atomic number for atoms, ions, and isotopes
  • Periodic table
    • Know the difference between groups (families) and periods.
    • Identify metals, metalloids (semimetals), and nonmetals
    • Determine charges of ions using the periodic table.
  • Mole concept
    • Convert between moles, mass, number of particles using molar mass and Avogadro’s number
    • Identify mole ratios in balanced chemical equations
Molecules, compounds, and chemical equations
  • Distinguish covalent versus ionic bonds
  • Understand chemical formulas
  • Nomenclature of ionic and covalent compounds, including some polyatomic ions (i.e. ammonium, carbonate, hydroxide, nitrate, phosphate, etc.)
  • Determine the formula mass or molar mass of a compound
  • Balance chemical equations
Lab skills
  • Choose the correct equipment for measurements (i.e. balance, graduated cylinder, Erlenmeyer flask, volumetric flask, beakers, buret, etc.)
  • Record measurements with the correct number of significant figures
  • Analyze data from lab measurements (i.e. mass, volume, etc.)
  • Evidence for chemical reactions
  • Graphing and data interpretation
    • Understand variables as physical quantities
    • Write an equation for the best-fit line in terms of physical quantities graphed
    • Interpret graphs
Math topics

(Includes basic math through college-level algebra)

  • Operations with Integers
  • Operations with fractions
  • Operations with decimals
  • Percentages
  • Ratios and proportions
  • Positive and negative integer exponents in calculations
  • Square roots
  • Order of operations
  • Scientific notation
  • Area of circle, square, rectangle
  • Averages (means, medians, and modes)
  • Substituting values into algebraic expressions
  • Setting up equations for given situations
  • Basic operations with polynomials
  • Solve equations for a variable

Taking the exam

Taking this exam is a two-step process:

  1. Register for exam

    Register with the Chemistry Department to be added to the D2L course that allows you access to the study materials and the link to the exam (the exam is only accessible once you are at the testing center for your appointment).

  2. Schedule exam

    Schedule a time to take the exam.

Testing procedure

The exam takes approximately 2 hours. Once you are at the testing center at your scheduled time you will log into this course and head to the exam which is located under the Quizzes tab. The testing center staff will type in the password to open the exam at which point you may begin.

You must have a valid picture ID when you come to the testing center. Scientific calculators are allowed during the exam. Graphing calculators will not be allowed. A periodic table will be provided to you at the testing center.

Contact information for the Testing Centers:

What if I don’t pass the exam?

If you do not pass the exam you may take the exam 1 more time. There must be at least 1 week between attempts. Please review for the exam before you retest. See the “reviewing for the exam” section above. If you do not pass the exam a second time please register for CH 151.

What if I pass the exam?

When you are finished with the exam you will need to show your exam score to a testing center representative. It will take at least 1 business day for your score to be entered. Once the score is entered you will be able to register for CH 221 provided you meet the other prerequisites listed above.


If you have any questions, contact: