Hi Dr. Bob,
I am quite stumped on how to figure out when chemical equations have a REACTION or NO REACTION. I have read the material in my textbook and even took out a chemistry books for the "Utterly Confused" to try to figure this out.
Example: Zn(s) + H3PO4(aq)--> Zn3(PO4)2(s) + H2. This has a reaction, but exactly how do I know that it has a reaction. Are there any tips that you can provide to easily be able to distinguish?
Thanks!
I have just what you need.
There are four rules that will help although it won' cover everything.
There are oxidation-reduction reactions that are not covered here although some are included here. Those are are another issue but will be covered when you cover redox equations.
Reactions will proceed from left to right (another way of saying a reaction will go to completion) if one of the following is true.
a. a gas is formed. Example:
Zn + 2HCl ==> ZnCl2 + H2. H2 is the gas.
b. a ppt is formed. Example:
AgNO3(a) + NaCl(aq) ==> AgCl(s) + NaNO3(aq)
That means you need to know what's soluble in water and what isn't. That's almost impossible except with many years of experience. However, here is a simplified set of rules. Note that AgCl is insoluble according to rule #3.
http://www.files.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html
Note, also, that just below that set of rules is a list of common gases other than H2.
3. Formation of of a slightly ionized substance. These are weak acids or weak bases (weak electrolytes) with the most common one you run into day to day is H2O. Example:
NaOH + HCl ==> NaCl + H2O
(You may hear from time to time that an acid + a base yields a salt + water. This neutralization reaction is such an example).
These three rules will handle probably 99% of what you will run into in the first year of chemistry. Some redox reactions are included in this group but not all of them. For example,
2CuO + C + heat ==> CO2(g) + 2Cu This redox equation still follws the rule of a gas being formed.
and Cl2 + 2KI ==> I2(s) + 2KCl is another one (I2 is a solid) but I don't think that is covered in the simplified rules.
Hi there! It's great to see your interest in chemistry. Understanding whether a chemical equation has a reaction or not can be determined by considering a few key factors. Let me explain the steps to you:
Step 1: Identify the reactants and products: In your example, the reactants are zinc (Zn) and phosphoric acid (H3PO4), while the products are zinc phosphate (Zn3(PO4)2) and hydrogen gas (H2).
Step 2: Check for balanced elements: Make sure that each element appears the same number of times on both sides of the equation. In your example, zinc (Zn) is balanced with three zinc atoms in the product side, and phosphorus (P) is balanced with two phosphorus atoms in the product side as well. Hydrogen (H) is balanced with four hydrogen atoms on both sides.
Step 3: Consider solubility and other properties: Certain compounds are insoluble, meaning they don't dissolve in water, and can be predicted to form a solid product. In your equation, zinc phosphate (Zn3(PO4)2) is insoluble, so it forms a solid.
Step 4: Evaluate the reaction conditions: Look for any special conditions mentioned in the equation, such as heat or a catalyst. These conditions can facilitate the reaction.
By following these steps, you can determine whether a reaction occurs or not. In the example you provided, since the reactants form products that fulfill all the above conditions, a reaction is expected to occur.
It is important to note that these steps provide a general guideline, but some reactions may require more advanced knowledge or experimental data to determine if they will occur. In those cases, further investigation or consultation with a more experienced chemist may be necessary.
I hope this explanation helps you understand how to determine if a chemical equation has a reaction or not! Let me know if there's anything else I can assist you with.