I am going to post this blog five times by the end of November (my goal being before Thanksgiving) to address five types of chemical reactions, Synthesis, Decomposition, Single Replacement, Double Replacement, and Combustion of a Hydrocarbon.
1. Predict the products of a Synthesis (or Combination) reaction.
2. Balance a chemical equation.
3. Identify the seven diatomic elements.
This type of chemical reaction was also discussed in the 01/16/2014 blog post about the "Combination of Magnesium & Oxygen" .
Predicting Products of chemical reactions uses the skill of Formula Writing, knowledge of the Diatomic Elements, and the skill of Balancing Equations to produce a final reaction.
A Synthesis Reaction (or Combination) is the chemical combination of one or more chemicals to produce one compound.
For an introductory chemistry student, I am focusing on the reaction of two elements to form one compound.
The brief video shown here is the reaction of iron with sulfur to form iron sulfide:
This is a simple reaction to write and balance:
Fe (s) + S (s) à FeS (s) + energy
It is an exothermic reaction so this concept can be discussed as well.
This reaction is easy to perform on top of wire gauze -- the wire gauze will be difficult to clean and may have to be thrown out after. This is also a smelly reaction producing iron oxide which smells like rotten eggs.
Fe (s) + O2 (g) à FeO (g)
This reaction shows oxygen gas in an elemental state where the element is more stable bonded to itself producing a diatomic molecule. There are seven elements found in a diatomic state – they are bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, and fluorine. An easy pneumonic to remember this is “BrINClHOF” . (sounds like brinclhoff)
Chemistry is the study of Matter and Energy and the changes they undergo. The Laws of Thermodynamics provide the parameters in which reactions will occur. The 1st Law of Thermodynamics states that matter and energy can neither be created nor destroyed but can only change forms.
To follow this 1st law of Thermodynamics, the number of atoms reacting (on the left side of the arrow of a reaction) must be the same as the number of atoms produced (on the right side of the arrow of a reaction).
In this reaction Fe (s) + O2 (g) à FeO , there is 1 atom of Fe and 2 atoms of oxygen reacting and 1 atom of iron and only 1 atom of oxygen produced. This reaction does not follow this 1st Law of Thermodynamics because it is not balanced.
To balance a chemical reaction, a chemist can only place numbers in front of a correctly written symbol or formula. Subscripts are not added to balance a reaction.
These numbers in front of a formula are called Coefficients and the number “1” is never written out as a coefficient. If the formula is written without a coefficient, there is one unit of that formula.
I’m sort of old-fashioned when it comes to balancing reactions, simply comparing reactants and products until it’s balanced, and I will offer some “tricks” along the way.
Here is one worksheet that focuses on Synthesis reactions and requires prediction of products (formula writing) and balancing of reactions. It also has the answers:
I will post 4 shorter posts through the end of the month of November to address the other types of reactions. I hope to have this done before Thanksgiving (11/27)!
Check out the Topic List to help you to find past Blog entries.
As the holidays approach, buy my lab book "Chemistry on a Budget" (or ask for it as a gift) -- it is available for $20 at amazon.com or $23 at lulu.com. It will take a few weeks to get to you, so order now!
This book contains 13 labs using consumable materials purchased from local stores. There are two versions of each lab, one with a ten-question conclusion and one with directions for a full lab report. This way the teacher has the option! Each lab is two pages to allow for one two-sided handout.
Have a good weekend!