Answer evaluation

When a student answer is evaluated against an author coded correct or incorrect answer the follow guidelines are followed.

• Brackets in a chemical formula are significant. Na2[MoOCl4] is not the same as Na2MoOCl4.
• Parentheses are significant. Zn(OH)4 is NOT equivalent to ZnOH4.
• Order of reagents (molecules on the left side of the reaction arrow) and of products (molecules on the right side of the reaction arrow) are NOT significant. is equivalent to .
• Reagents and products are not interchangeable, even if the reaction is in equilibrium. is not equivalent to .
• A superscript and subscript adjacent to each other is NOT equivalent to the isotope template .
• A single subscript, superscript, or stacked superscript/subscript to the left or right of a chemical symbol is a significant modifier of the chemical symbol/formula.
• Case is significant. Co is not equivalent to CO.
• The coefficients on each reagent/product are significant. Coefficients must appear in front of the corresponding reagent/product. 2O2 is not O22.
• The word "heat" is a special reagent/product that is case-insensitive.
• The order of elements in a compound is significant. N2O is not the same as ON2.
• A correct/specific incorrect answer may consist of: a single chemical symbol/formula, multiple chemical symbols/formulas connected by "+" signs, or a complete chemical equation.
• Correct and specific incorrect answers are not limited to contain valid chemical symbols. For example, an author may script an answer involving the chemical "X" as a placeholder.
• A state marker in a subscript is equivalent to a state marker that is not subscripted. Thus, the following are equivalent:
  • and .
  • and
• An overbar applied to a symbol+subscript is equivalent to an overbar applied to a symbol, followed by a subscript.
  For example, the following are equivalent: and (difference is slight but look at center of overbar to see that in second example it is centered over the nu and subscript while in the first example it is only over the nu).
• The following are considered equivalent (with and without the subscript 'e'):
  • 
  • 
• Note that the following notation is not recognized as acceptable: .
• The following particles and mass/charge prefixed particles are NOT considered equivalent:
  • 
  • 
  • 
  • 
  • 
  • 

• If you want to allow either or to be marked correct, you will have to code both expressions as alternate correct answers. You should not code for every possible combination of particle and mass/charge particle notation. Good form dictates that a student should use all one type of notation.

See also:

Generic incorrect answer responses