Chemical+Equations


 * Chemical Equations **

A chemical Equation is an equation that represents a chemical reaction taking place. It shows the reactants that are reacting with each other and the products that are formed. For example when sulphur reacts with oxygen in the air to form Sulphur dioxide.

S + O 2 ---> SO 2

This reaction shows the reactants and the products which they form. 

Another Example is as here below:

Every chemical equation has several features which are discussed here below using the above example for reference.
 * nnnnnnnnnnnnnnnnn || nnnnnn || nnnnnnnnnnnnnnnnnnn || nmmmm ||  || nnnnn || nnnnnnnnnnnnn ||
 * Mg(OH) 2 (aq) || + || 2HCl(aq) || ---> || MgCl 2 (aq) || + ||  2H 2 O (l) ||
 * Magnesium Hydroxide || + || Hydrochloric acid || <span style="display: block; font-family: Tahoma,sans-serif; font-size: 19px; text-align: center;">---> || <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Magnesium chloride || <span style="display: block; font-family: Tahoma,sans-serif; font-size: 19px; text-align: center;">+ || <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">water ||

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">** 1. ** The reactants are written on the left side while the products are given on the right side of the equation.

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> **2.** The arrow sign is important

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">If you have an arrow pointing in one direction only then the reaction goes from the reactants to the products. (All the reactants react with each other to from the product. The products cannot react with each other to reform the reactants)

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">If you have an arrow pointing in two directions then the reaction can happen in both directions (The products can react to reform the reactants). //(more of this will be discussed in topic 7-equilibrium)//

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">** 3. ** The subscripts shows the number of particles of that atom which are present in the molecule. (in the case of MgCl 2 the number 2 shows that each molecule has two Cl atoms)

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">** 4. ** The number in front of the molecule shows the number of those molecules that react. So, in the above reaction 1 molecule of Mg(OH) 2 reacts with 2 molecules of HCl to form one molecule of MgCl 2 and two molecules of 2H 2 O. (this number also shows the mole ratio of the species-‘reactants and products’-in the reaction)

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">** 5. ** Another important thing is the state symbol which shows what state the molecule is in; These are the four state symbols that are used: <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> **S-** solid <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> **l-** liquid <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> **g-** gas <span style="font-family: Tahoma,sans-serif; font-size: 14pt;"> **aq-** aqueous (meaning dissolved in water) <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">In the above example the reactants and the salt MgCl 2 are in aqueous form which means that they are dissolved in water. //<span style="color: #e71313; font-family: Tahoma,sans-serif; font-size: 14pt;">Note: these state symbols are only used sometimes when it is necessary for you to know the state of the species in the reaction. //

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">It is very important to ensure that a chemical equation is always balanced. Look at the equation below: <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">SO 2 + Mg ---> S + MgO

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Can you figure out what is wrong with the above equation? <span style="font-family: Tahoma,sans-serif; font-size: 14pt;">There are two Oxygen atoms on the reactants side and only one on the products side. What this suggests is that one of the oxygen atoms has mysteriously disappeared! But that’s not possible. What you need to do is to balance the equation.

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Add a two in front of the Magnesium oxide: 2MgO

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">But now we have 2 Mg on the right side but only one on the left. So add a 2 in front of the Mg: 2Mg

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">Now the equation is balanced:

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">SO 2 + 2Mg ---> S + 2MgO

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">The number of each atom on both sides is the same.

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">As I said earlier, the number in front of the species shows the moles of each species that reacts or which is formed. If you look at the above equation you’ll see that the ratio is 1 SO 2 to 2 Mg, which means that 1 mol of SO 2 is required which reacts with 2 mol of Mg to from 1 mol of S and 2 moles of MgO.

<span style="font-family: Tahoma,sans-serif; font-size: 14pt;">This is especially useful when you are dealing with calculations involving finding the amount of a product that you expect to be formed in a given reaction. //That is in the topic that follows//.


 * <span style="color: #0006ff; font-family: Tahoma,sans-serif; font-size: 110%; line-height: 27px;">By the end of this lesson you should be able to: **
 * **<span style="color: #0006ff; font-family: Tahoma,sans-serif; font-size: 110%; line-height: 27px;">Write a chemical equation when you are given the reactants and the products and to balance this equation **
 * **<span style="color: #0006ff; font-family: Tahoma,sans-serif; font-size: 110%; line-height: 27px;">Identify the mole ratio of two species in a chemical reactions **
 * **<span style="color: #0006ff; font-family: Tahoma,sans-serif; font-size: 110%; line-height: 27px;">To use the state symbols, (s), (g), (l), (aq). **

<span style="font-family: Tahoma,sans-serif; font-size: 19px; line-height: 27px;">media type="facebooklike" key="http%3A%2F%2Fibchem4u.wikispaces.com%2FChemical%20Equations" width="360" height="64"

<span style="font-family: Tahoma,sans-serif; font-size: 19px; line-height: 27px;">