2009 1 August Chemistry Chemical Changes Post THREE
Alright! Good! We're coming to the last two section of the Five Major Chemical Reaction! So let's not delay! Also called Single Displacement, Single Subsitution or Activity Replacement. Single Replacement, as the name suggests, is basically one component of a compound "going" to the other. For example, if we place a piece of copper into a silver nitrate solution, slowly, you would see that the copper begins to turn into a silvery-white material, and the solution begins to turn from light silver into blue. What is actually happening is that the silver from the silver nitrate solution is "going" to the copper, hence, we can represent Single Replacement with a simple equation. AB and C -> A and CB Or in the previous case, the copper and silver nitrate solution can be represented like this. 2 AgNO3 + Cu -> Cu(NO3)2 + 2 Ag There are two types of Single Replacement, mainly cationic and anionic Single Replacements. In an cationic Single Replacement, ions are produced, while in an anionic Single Replacement, ions are not produced. The above reaction would be considered cationic as it is likely to make cations. An example of anionic reaction would be bubbling chlorine gas in a potassium iodine solution, the chlorine is used up and the solution turns purple-brown because of the iodine. Also represented as, 2 KI + Cl2 -> 2 KCl + I2 Now that we have finished Single Displacement, I will move on to Double Displacement. As we have said just now, Single Displacement is the component of a compound "going" to another compound or element, in Double Displacement (also called Double Replacement or Metathesis), instead of "going" to the other compound or element, it switches place with another component of the other compound. One common example would be hydrochloric acid (acid) and sodium hydroxide (base) would neutralize each other (as one is acidic and one is alkaline) to make water and salt. This can be written in this way. HCl + NaOH -> HOH + NaCl Hence, we can simply write Double Displacement as... AB and CD -> AD and CB Now that we have finished all five major chemical reactions, you might be wondering, how can some of this happen? One major thing would be bonding. And that is what we are moving on to next. Have you ever wondered even though the Periodic Table only has 118 elements, why are there so many we see in our everyday life? This is so as the elements can bond together to make other elements. So in this case, why do bonding happen? And how does bonding occurs? It is said that atoms with less than 8 valence electrons will bond together with other atoms to "complete" the full 8 valence electrons. In the periodic table, different groups of metal are classified according to their different valence electrons. Group One has 1 Valence Electron. Group Two has 2 Valence Electron. Groups Three to Twelve have Electrons that are normally not easy to count with the orginial way. Group Thirteen has 3 Valence Electons. Group Fourteen has 4. Group Fiveteen has 5. Group Sixteen has 6. Group Seventeen has 7. Group Eighteen has 8 or 2. (in the case of Helium, it is 2) An simple bond would be between sodium and chlorine gas, which would result in the table salt of what we have now. So how is bonding done? Well, it is exactly the same as magnets. The negatively charged electrons would attract the positively charged protons, and it completes the bond this way. A amount of energy or heat is needed to separate these bonds. Now that I have come to the end of the introduction to Bonding, we will be talking more about elements, and of course, the two different types of bonding I am going to touch on would be Ionic Bonding and Covalent Bonding. Link One Link Two Link Three Glossary Cation A positively-charged ion. Valence Electron The number of electrons on the outmost shell of a certain element. |
By Zhan Peng from 2-6 Catholic High School Class 2-6 One Golden Rule NOTHING |