Common wrong-answer feedback for chemical formula answers

Updated 30 Aug 2024

You may be able to make use of one or more of the following wrong-answer feedback responses as you edit or create chemical formula or expression answers in the Simple Editor.

If a submission contains a template with an empty input field, give the unpenalized response: "There is an error in your submission. Make sure you have entered a value or symbol in each formatting box."

Example: A fraction in which the numerator or denominator is blank or a stacked sub/superscript in which either the super or subscript is blank.

 

If a submission would be correct except that text that should appear in a subscript instead appears as regular text, give the unpenalized response: "Use subscripts to represent the number of each type of atom or ion in a molecule."

Example: Entering "C2H40" instead of C subscript 2 H subscript 4 O

 

If a submission would be correct except that a superscript/subscript pair appears where a stacked super/subscript should appear or vice versa, give the unpenalized response: "Check your placement of subscripts and superscripts."

Example: Entering CO superscript 2- over 3 instead of CO subscript 3 superscript 2-

 

If a submission would be correct except that a superscript of the form "+#" or "-#" in the submission appears as "#+" or "#-" in the correct answer, give the unpenalized response: "Express charges as [#+], not [+#]." with the bracketed text replaced as appropriate to the specific submission/answer pair.

 

Similarly, if the submission contains a superscript of the form "1+", "+1" or "1-", "-1" where the correct answer has simply "+" or "-", give the unpenalized response: "Express single charges as [+], not [1+]" with the bracketed text replaced as appropriate to the specific submission/answer pair.

 

If a submission would be correct except for having an incorrect order of elements in one or more compounds, give the penalized response: "Check that you have the proper order for the element symbols in your answer."

 

If a submission contains a minus sign between two reagents or products, give the response: "Minus signs are not permitted between reagents or products in chemical formulas." Note: minus signs in a subscript or exponent are permitted.

 

If a superscript and subscripted number is detected prefixed to an element, but the two are not stacked, give the unpenalized response: "Check your placement of subscripts and superscripts. Use the Super/Subscript button for isotopes."

 

When stacked super/sub script is used for phases or when a phase is placed before an ion charge, give the unpenalized response "Check your placement of subscripts and superscripts. Place phases at the end of a chemical formula."

Example: Ba(aq) superscript 2+ plus SO(aq) superscript 2- right arrow BaSO subscript 4 (s) and CO superscript 3- subscript aq in parentheses

 

If a submission would be correct were cases not significant, give the response: "Check the capitalization of the chemical symbols in your answer." Example: user submits co2 when the correct answer is CO2.

 

If the submission is a reaction and the reagents/products are correct but the coefficients are not in the correct ratio, give the penalized response: "Your answer is not a balanced chemical equation".

Example: user submits H subscript 2 O right arrow H subscript 2 + O subscript 2 when the correct answer is 2H subscript 2 O right arrow 2H subscript 2 plus O subscript2 .

 

If the submission is a reaction, the reagents/products are correct, and the coefficients are in the correct ratio but not equal to the coefficients in the coded answer, give the penalized response: "Check the coefficients in your chemical equation."

Examples:

Student submits 4H subscript 2 O right arrow 4H subscript 2 plus 2O subscript 2 when the correct answer is 2H subscript 2 O right arrow 2H subscript 2 plus O subscript 2 .

Student submits 4H subscript 2 O right arrow 4H subscript 2 plus 2O subscript 2 when the correct answer is H subscript 2 O right arrow H subscript 2 plus one half O subscript 2 .

Student submits 2 H subscript 2 O right arrow 2 H subscript 2 plus O subscript 2 when the correct answer is H subscript 2 O right arrow H subscript 2 plus one half O subscript 2 .

Student submits H subscript 2 O right arrow H subscript 2 plus one-half O subscript 2 when the correct answer is 2H subscript 2 O right arrow 2H subscript 2 plus O subscript 2 .

 

If a student includes a coefficient of 1 on any atom, ion, molecule, particle, give the unpenalized response: "Coefficients of 1 are not allowed. To indicate a coefficient of 1, do not include a value."

Example: Student enters 2H subscript 2 plus 1O subscript 2 right arrow 2 H subscript 2 O when the correct answer is 2H subscript 2 plus O subscript 2 right arrow 2H subscript 2 O.

 

If your coded answer includes a phase for one or more reagents/products and the submission does not include a phase for the same reagent/product, give the penalized response: "Check that you have properly identified all of the phases in your answer."

Example: Student submits 2 H subscript 2 O right arrow 2 H subscript 2 plus O subscript 2 when the correct answer is 2H subscript 2 O (aq) right arrow 2H subscript 2 (g) plus O subscript 2 (g).

 

If the submission includes a phase for one or more reagents/products and the coded answer does not include a phase for the same reagent/product, give the unpenalized response "Please enter your answer without phases."

Example: Student submits 2H subscript 2 O (aq) right arrow 2H subscript 2 (g) plus O subscript 2 (g) when the correct answer is 2H subscript 2 O right arrow 2 H subscript 2 plus O subscript 2.

 

If a submission would be correct except that the wrong state markers were used on one or more compound, then give the penalized response "Check that you have properly identified all of the phases in your answer." For example, student uses (s) where the correct answer has (aq).

 

If a submission contains unrecognized state markers that fall into one of the categories below, then give the unpenalized response "Check that you have properly formatted all of the phases in your answer."

Examples: Student uses (1) "one" instead of (l) "ell" to represent a liquid phase or uses a capital instead of lowercase state marker, e.g. (S) vs (s).

 

If the submission is a reaction, the reagents/products and coefficients are correct, but the wrong type of reaction arrow is used, give the unpenalized response "Check the reaction arrow in your chemical equation."

See also:

Chemical formula or expression (answer type) | Add and edit wrong-answer feedback