Create chemPad Questions for Reactions

When you create chemPad questions that are answered with a reaction expression, your students can enter the order of compounds (with their coefficients) differently from the answer key in either the reactants or the products. For example, O₂ + CH₄ → CO₂ + H₂O is considered equivalent to CH₄ + O₂ → H₂O + CO₂. Your students can also enter solvate dot notation if needed.

You can choose whether to allow alternative reaction arrows in your students' responses. You can require your students to use the reaction arrow specified in your answer key, allow them to use any reaction arrow, allow either an equilibrium arrow or a right arrow, or allow either an equilibrium arrow or a left arrow.

Note Do not specify answer keys containing the < or > characters directly in Answer, as these characters might be interpreted as the start or end of a tag. Instead, assign your answer key to a variable and reference the variable as described in this topic.

Click Questions > Create. The Question Editor opens.
In Name, type a name for the question.
In Mode, select Fill-in-the-Blank.

In Question, add the following code, replacing answer_key with your answer key:

<eqn>
$mykey='answer_key';
''
</eqn>

This code assigns your answer key to the variable $mykey. You can use a different variable name if needed.

For example:

Answer	Code
CH₄ + 2 O₂ → CO₂ + 2 H₂O	`<eqn> $mykey='CH_{4} + 2 O_{2} --> CO_{2} + 2 H_{2}O'; '' </eqn>`
2 SO₂ + O₂ ⇌ 2 SO₃	`<eqn> $mykey='2 SO_{2} + O_{2} <=> 2 SO_{3} '; '' </eqn>`
H₃PO₄(`aq`) + 3 NaOH(`aq`) → 3 H₂O(`l`) + Na₃PO₄(`aq`)	`<eqn> $mykey='H_{3}PO_{4}(aq) + 3 NaOH(aq) --> 3 H_{2}O(l) + Na_{3}PO_{4}(aq)'; '' </eqn>`
4 NO(`g`) + O₂(`g`) ← 2 N₂O₃(`g`)	`<eqn> $mykey='4 NO(g) + O_{2}(g) <=> 2 N_{2}O_{3}(g)'; '' </eqn>`

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.

In Answer, type the following items on a single line:

<EQN $PAD='chem'; $CHEM='method'; $mykey>

where method is one of the following chemPad parsing methods:

Reaction Type	Allowed Reaction Arrows	Method
Any	Only the reaction arrow specified by the answer key.	`rxn`
Equilibrium	→ or ⇌ or ←	`rxn,equ`
Product-favored	→ or ⇌	`rxn,eqr`
Reactant-favored	← or ⇌	`rxn,eql`

For example:

Answer	Code
CH₄ + 2 O₂ → CO₂ + 2 H₂O	`<EQN $PAD='chem'; $CHEM='rxn'; $mykey>`
2 SO₂ + O₂ ⇌ 2 SO₃	`<EQN $PAD='chem'; $CHEM='rxn,equ'; $mykey>`
H₃PO₄(`aq`) + 3 NaOH(`aq`) → 3 H₂O(`l`) + Na₃PO₄(`aq`)	`<EQN $PAD='chem'; $CHEM='rxn,eqr'; $mykey>`
4 NO(`g`) + O₂(`g`) ← 2 N₂O₃(`g`)	`<EQN $PAD='chem'; $CHEM='rxn,eql'; $mykey>`

By default, your students must specify each chemical formula exactly as listed in your answer key. To allow specific kinds of notation, you can add a comma and one of the following methods after rxn, rxn,equ, rxn, eqr, or rxn,eql:

Notation	Example	Method
Formula elements in any order	CH₄N₂O or CN₂H₄O	`fmla`
Condensed formulas	(NH₂)₂CO or CH₄N₂O	`fmla,index`
Nuclear particles and nuclides	${}_{1-}^{0}β$ or ${}_{1-}^{0}e$	`nclr`
Nuclear particles with charges	${}_{2}^{4}{He}^{2 +}$	`nclr,ion`
Ion charges	Mg²⁺ or Mg⁺²	`ion`
Ionizable protons first	CH₃CO₂H or HCH₃CO₂	`ion,acid`

For example:

<EQN $PAD='chem'; $CHEM='rxn,equ,fmla,index'; $mykey>

Note

You do not need to specify the solvate mode for your students to enter solvate dot notation.
Specify methods only in the order listed here.
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 example:
```
<EQN $PAD='chem'; $CHEM='rxn'; $mykey> {tab} <EQN $mykey2>
```
For information about how to specify chemical notation in your answer key, see Creating chemPad Answer Keys.

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.
Click Test/Preview to test the appearance and behavior of the question. See Test Questions.
Click Redisplay to show certain kinds of errors in the Display section of the Question Editor. Make any needed changes to your question.
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.
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 (Reaction)

The following table summarizes an actual question.

QID	`1534317`
Name	`Template2 5.CHEMP.07.`
Mode	`Fill-in-the-Blank`
Question	`<eqn> $mykey='2 HCl + CaCO_{3} --> CaCl_{2} + CO_{2} + H_{2}O'; '' </eqn> Show the reaction between hydrochloric acid and calcium carbonate that produces calcium chloride, water, and carbon dioxide. (<p:lowcoeff> Omit states-of-matter in your answer.)<br> <_>`
Answer	`<EQN $PAD='chem'; $CHEM='rxn'; $mykey>`
Display to Students

Example chemPad Question (Reaction)

The following table summarizes an actual question.

QID	`1534332`
Name	`Template2 5.CHEMP.08.`
Mode	`Fill-in-the-Blank`
Question	`<eqn> $mykey='C_{5}H_{5}N(aq) + H_{2}O(l) <=> C_{5}H_{5}NH^{+}(aq) + OH^{-}(aq)'; '' </eqn> Write the reaction for pyridine, <h:chemical>C_5H_5N</h:chemical>, acting as a base in water. (<p:lowcoeff> Include states-of-matter under SATP conditions in your answer.)<br> <_>`
Answer	`<EQN $PAD='chem'; $CHEM='rxn,ion,acid'; $mykey>`
Display to Students

Example chemPad Question (Nuclear Equation)

The following table summarizes an actual question.

QID	`1534326`
Name	`Template2 5.CHEMP.09.`
Mode	`Fill-in-the-Blank`
Question	`<eqn> $mykey='^{131}_{53}I --> ^{0}_{-1}beta + ^{131}_{54}Xe'; '' </eqn> Write the nuclear equation for beta decay of Iodine-131. (<p:lowcoeff> Omit states-of-matter in your answer.)<br> <_>`
Answer	`<EQN $PAD='chem'; $CHEM='rxn,nclr'; $mykey>`
Display to Students