Create chemPad Questions for Kinetic or Equilibrium Expressions

When you create chemPad questions that are answered with a kinetic or equilibrium expression, your students can change the order of compounds (with their exponents) relative only to their position in a fraction.

For example, answer format example 1 is considered equivalent to answer format example 2. Your students can also enter multiplication or solvate dot notation if needed.

  • When your students enter subscripted or superscripted letters in chemPad, they must enclose the subscript or superscript in braces {} to receive credit. For example, to enter Kb, your students must type K_{b}.
  • Your students must specify solvate dots in their responses. However, if they omit multiplication dots, their responses will still be scored correctly.

To create a chemPad question for which the answer is a kinetic or equilibrium expression:

  1. Click Questions > Create. The Question Editor opens.
  2. In Name, type a name for the question.
  3. In Mode, select Fill-in-the-Blank.
  4. In Question, type your question. Provide relevant information about assumptions or expectations for the question, for example, the conditions for the question — STP, SATP, or reaction/prevailing conditions — or whether states-of-matter should be specified in the response. Use the answer placeholder string <_> to specify where the answer box should be displayed.
  5. In Answer, type the following items on a single line: 
    <EQN $PAD='chem'; $CHEM='rqn'; ''>answer_key 

    where answer_key specifies the correct answer to the problem, and method is one of the following chemPad parsing methods:    




    Formula elements in order specified by answer key



    Formula elements in any order

    CH4N2O or CN2H4O


    Condensed formulas

    (NH2)2CO or CH4N2O


    Ion charges

    Mg2+ or Mg+2 


    Ionizable protons first

    CH3CO2H or HCH3CO2 


    For example:  



    answer format example 1
    <EQN $PAD='chem'; $CHEM='rqn,ion'; ''>
    K_{b} = [OH^{-}] . [C_{5}H_{5}NH^{+}] / 
    • If an answer extends beyond the right side of the Answer box, it is wrapped to the next line, but it is still considered a single line so long as you do not press ENTER.
    • As with other fill-in-the-blank questions, you can specify alternative answer keys separated by the characters {tab}.
    • For information about how to specify chemical notation in your answer key, see Creating chemPad Answer Keys.
  6. Optional: Type a Solution.

    The solution helps your students understand the steps they need to take to determine the correct answer to the question. Your assignment settings specify when to show the solution.

  7. Click Test/Preview to test the appearance and behavior of the question. See Test Questions.
  8. Click Redisplay to show certain kinds of errors in the Display section of the Question Editor. Make any needed changes to your question.
  9. Optional: Click Show Additional Information and change the question's sharing permission or add descriptive information.
    • By default, other instructors can use your question only if you provide them with the question ID, and only you can edit the question or find it in search results. To change the permission, see Share Questions With Other Instructors.
    • If you make your question publicly available, you might want to provide descriptive information to help others search for it. See Add Search Metadata to Questions.
  10. When your question displays and functions correctly, click Save.

    WebAssign assigns it a unique question ID (QID), which is displayed in parentheses after the question name.

    You can use your question in an assignment and see it in your My Questions list only after it is saved.

Example chemPad Question (Equilibrium Expression)

The following table summarizes an actual question.




Template2 5.CHEMP.10.




Write the <i>K</i><sub>b</sub> equilibrium expression for 
pyridine, C<sub>5</sub>H<sub>5</sub>N, acting as a base in 
water. (<p:lowcoeff>  Omit states-of-matter in your 


<EQN $PAD='chem'; $CHEM='rqn,ion,acid'; ''>K_{b} = [OH^{-}] . 
[C_{5}H_{5}NH^{+}] / [C_{5}H_{5}N]

Display to Students

Question as displayed to students