Help with working out chemical equations

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In summary, the conversation is about a user seeking help with chemistry equations for a social relevance essay on forensic chemistry. The specific focus is on the Dermal Nitrate Test and the use of redox indicators such as diphenylamine and luminol. The user is also seeking assistance with other equations, including the Sodium Rhodizonate Test and the Modified Griess Test.
  • #1
im new to this forum, i have used it quite a lot for physics, however i need some help with chemistry and was hoping someone could help me work out a few equations i need for a social relevance essay. I am doing the essay on forensics chemistry; particularly how gunshot residue is detected. The first equation i need help with is from the Dermal Nitrate Test, and so far i only know the reactants, not the products,

Nitrocellulose + Diphenylamine + Concn Sulfuric Acid --->
C6H8(NO2)2O5 + (C6H5)2NH + H2SO4 --->

i have a couple others i need help with, but I am unsure of all the reactants at the moment, so i will post them up when i have them (Sodium Rhodizonate Test & the Modified Griess Test if anyone knows of them)

thanks a lot for any help,
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  • #2
diphenylamine is a redox indicator, its purple when oxidized and colorless when reduced.

the acid helps keep it reduced - the presence of an oxidizer such as nitrocellulose will oxidize the diphenylamine (despite the strong acid) and change color.

many of the chemical methods used in forensic chemistry make use of redox indicators of varying strengths/preferences. another one that you might be interested in is luminol, which with H2O2, will illuminate when reduced by something such as Fe (thereby used to detect blood).
  • #3
wow thanks quetzacoatl, i hadnt seen anything about the 'luminol test', however it sounds like it will fit in nicely with my essay.

Anyone else able to offer any assistance? particularly in the equations as i am hopeless at doing them, which is not good as according to my chem teacher they are important for this essay,

1. What is a chemical equation?

A chemical equation is a symbolic representation of a chemical reaction, which shows the reactants and products involved in the reaction, as well as the relative quantities of each substance. It follows the law of conservation of mass, meaning that the total mass of the reactants must equal the total mass of the products.

2. How do I balance a chemical equation?

To balance a chemical equation, you need to make sure that the number of atoms of each element on the reactant side is equal to the number of atoms of the same element on the product side. This can be done by adjusting the coefficients (numbers in front of the chemical formulas) of each substance. It is important to remember that you cannot change the subscripts (numbers within the chemical formulas) as this would change the identity of the substance.

3. What is the purpose of balancing a chemical equation?

The purpose of balancing a chemical equation is to accurately represent the reactants and products involved in a chemical reaction, as well as the relative quantities of each substance. This allows scientists to understand the stoichiometry (proportions) of the reaction and predict the amount of product that will be formed from a given amount of reactants.

4. Can a chemical equation have fractions as coefficients?

No, a chemical equation should always have whole number coefficients to represent the number of molecules involved in the reaction. If you end up with fractions when balancing the equation, you should multiply all coefficients by the lowest common denominator to get rid of the fractions.

5. Are there any rules to follow when writing a chemical equation?

Yes, there are some general rules to follow when writing a chemical equation. The reactants should be written on the left side of the arrow and the products on the right. The arrow represents the direction of the reaction, with the reactants being transformed into products. The state of matter (solid, liquid, gas, aqueous) should also be included for each substance. In addition, charges should be balanced on both sides of the equation.

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