UP Board Class 12th Chemistry paper 1 is scheduled to be held on February 20, 2018, and Paper 2 will be held on February 22, 2018. Students find chemistry a difficult subject because of the chemical equations, methods and reactions of molecules, reactants and atoms etc. However, if they understand the basics of any concept, it will be easier for them to carry out the chemical equations. Therefore, students are first advised to learn the basics of every concept i.e. the formula, method, definition etc. Here students can learn how to balance the chemical equations in the simpler method by learning the law of conservation of mass. According to this law, neither a molecule can be produced nor destroyed in a chemical reaction.
To understand this, students can go through the following reaction which mentions oxidation of butane molecule and it results in carbon dioxide and water.
To balance the equation as mentioned above, students can follow the steps given below –
Step 1. First, write the number of molecules of elements on both sides. To find out the number of molecules in the equation, check the numbers of each molecule –
(a) Write the number of left molecules
C = 4, H = 10 and O = 2
(b) Write the number of right molecules
C = 1, H = 2 and O = 3
Step 2. Now, select the element in which the reactants and only one molecule appear in the products. As mentioned above, hydrogen and oxygen are more than carbon dioxide. So you have to balance the carbon molecule first.
Step 3. To balance carbon, multiply 4 by the carbon on the right side. After which, you will get number of carbon molecules same on both sides. However, students should remener that in any chemical equation you can the properties, but cannot change the encircled. Check the image below for step 2 and 3 -
Step 4. To balance the carbon, multiply the carbon molecule by 4, this will result in making the number of carbons equal on both sides, and also, the number of oxygen molecule will become 9 from 3. Check the image below -
When the multiplier on the right side of the carbon is multiplied by 4 the oxygen 2 and 8 is obtained and then remaining 1 oxygen is added to H2O and oxygen 9 is obtained.
Step 5. Now the hydrogen molecule needs to be balanced. For this, Hydrogen 10 on left therefore you need to have hydrogen 10 on the right.
C4H10 + O2 --> 4CO2 + 5H2O
We have multiplier 5 because there are 2 hydrogen molecules as shown below
When we multiply, hydrogen 2 by 5, then we get Hydrogen 10.
Step 6. Now, the oxygen molecules of the equation need to be balanced as mentioned in the image below -
On the left side of the equation, multiply oxygen molecule by the factor of 13/5. Now you will have 13 oxygen molecules on both sides.
Some important tips:
- First, see the number of molecules of elements on either side in the equation.
- To find out the number of molecules in the equation, see number of each molecule and then start balancing them at same time
- While balancing an element, cross-check what are the changes being made into other elements as a result