Balancing Chemical Equations
When a reaction occurs, The Law of Conservation of Matter must always be obeyed. In order to do this, we must balance chemical equations to show that no matter was lost or gained. To balance an equation, there is a series of steps that must be followed, starting with writing the correct formula for all reactants and products. When doing this step, keep in mind the diatomic elements. Next, you adjust the coefficients to equal the number of atoms on both sides. The best strategy for doing this step is to adjust the coefficient of the single species last. Additionally, it is okay to temporarily use fractions for the coefficient if needed.
Types of Chemical Reactions
Chemical reactions are occurring all around us everyday, and believe it or not there are many different types of chemical reactions - five to be exact:
1. Synthesis/Combination
- In a synthesis reaction, there is always only one product formed. In order for this to happen, I've discovered that the reactants must include one cation and one anion, which will usually be a metal and non-metal, but not always.
- A + X = AX
2. Decomposition
- In a decomposition reaction, a substance does just that, decomposes. One reactant will always form two products in a decomposition reaction.
- AX = A + X
3. Single Replacement
4. Double Replacement
- For a single replacement reaction, there is always both a compound and an element in both the reactants and products sides of the arrow.
- If the element is a metal, it will replace the cation in the compound while if the element is a non-metal, it will replace the anion in the compound.
- A(+) + B(+)X(-) = B + AX or Y(-) + B(+)X(-) = X + BY
- A double replacement reaction occurs if both the reactants and products sides of te reaction arrow have two compounds; in oter words, two compunds will react and form two new compunds.
- The two positive ions, or cations will replace each other or basically switch. The anions will switch as well.
- A(+)Y(-) + B(+)X(-) = BY + AX
5. Combustion
Single Replacement Reaction - Activity Series
- Combustion reactions will always form Carbon Dioxide and Water as their products, and will always have Oxygen as a reactant and a given amount of Carbon and Hydrogen as reactants as well.
- Hydrocarbons
- CxHy(O2) = CO2 + H2O
Beaker 1 Beaker 2
In single replacement reactions, when the element replaces one of the elements in the compound, a reaction will only take place if the element which is doing the replacing has a higher activity than the element it is replacing. For example, if the reactants are Copper and Magnesium Chloride, no reaction will take place since Copper has a lower activity level than Magnesium, so it can't displace it to make a reaction occur (as shown above in beaker 2). However, in a reaction where Aluminum and Copper Chloride are the reactants, a reaction will occur since Aluminum has a higher activity level than Copper. The products in this example will be Copper and Aluminum Chloride (as shown above in beaker 1). Furthermore, if the element in the reaction is a metal with a higher activity level than Hydrogen, it will displace hydrogen from Hydrogen Chloride or Hydrogen Sulfate. Additionally, if the element is a metal with a higher activity level than Magnesium will displace hydrogen from water in a reaction. Lastly, if the element has a higher reactivity than Silver, it will combine directly with oxygen in a synthesis reaction. The only elements that will not do this are silver, platinum, and gold. I found this interesting because this explains why they make jewelry out of these three elements since they won't combine with oxygen.
Personal Reflection and Thoughts
While performing labs and going through problems dealing with these three new concepts, I found it interesting to figure out why only some reactions work when completing the activity series worksheet. Also, I enjoyed balancing equations because I like to have to figure out problems like that. In the future, I'm looking into chemical engineering, so this unit was really interesting to me because it made me realize why certain things can only be made out of certain material. For example, I realize that we use iron for ships since it won't have a reaction with water while something else might. I also found it interesting to find out that only silver, platinum, and gold don't react with oxygen because this explains why they make jewelry out of these three elements since they won't combine with oxygen and become dull.
