Chemical Reaction and Equation

15.What is a balanced chemical equation? Why should chemical equations be balanced?
Answer:
A balanced chemical equation is one in which the total number of atoms of each element are equal on both sides of the equation. A chemical equation is balanced so that the numbers of atoms of each type involved in a chemical reaction are the same on the reactant and product sides of the equation.
A balanced chemical equation satisfies the law of conservation of mass, i.e., the total mass of the reactants is equal to the total mass of the products.

balanced chemical equation

16.Write the steps involved in writing a balanced chemical equation.
Answer:
Step 1:
Know the reactants and products of the given chemical reaction and write down the word equation for the reaction. Note that the reactants must be written on the left hand side while the products must be written on the right hand side.
Step 2:
The second step is to write the skeletal equation. Write down the symbol and formula of each of the reactants and products.
Step 3:
Enclose the formula of each reactant and product in separate boxes and do not change the formula or the subscripts of anything inside the boxes while balancing the equation.
Step 4:
List the number of atoms of different elements on LHS (reactants) and RHS (products) separately.
Step 5:
Start balancing with the compound (either on the reactants side or on the products side) that contains the maximum number of atoms. After choosing the compound, select the element that has the maximum number of atoms. To balance the atoms, put a small whole number coefficient before the formula of the compound.
Step 6:
Balance all the elements one by one similarly. Check for the correctness of the balanced equation by counting and comparing the number of atoms of each element on both sides of the equation.
Step 7:
Write the physical state of each of the reactants and products.

involved in writing a balanced chemical equation

Check here-SSLC Karnataka State Board Science Important Question and Answer Chemical Reaction and Equation

17.Iron reacts with water (steam) forming iron oxide and hydrogen gas. Write a balanced chemical equation for this reaction.
Answer:
Step 1:
Let us write the word equation:
Iron + Water → Iron oxide + Hydrogen
Step 2:
Let us write the skeletal equation for the reaction using symbols and formulae:
Fe + H
2
O → Fe
3
O
4
+ H
2
Step 3:
Let us put all the formulae/symbols in separate boxes.
Step 4:
Let us list the number of atoms of each element on both sides of the equation:
Step 5:
We shall start with the compound having the highest number of atoms namely iron oxide. In this compound, let us start with oxygen as the number of oxygen atoms is highest in the compound.
There are four oxygen atoms in iron oxide on the RHS. However, there is only one oxygen atom on the LHS. To balance this, we shall put 4 as the coefficient for water (H
2
O).
Now let us balance the iron atoms. This can be done by putting 3 as the coefficient for Fe on the LHS. Now let us balance the hydrogen atoms. This is done by putting 4 as the coefficient for H
2
on the RHS. Now the equation becomes 3 Fe + 4 H
2
O → Fe
3
O
4
+ 4 H
2
Step 6:
Let us now check for the correctness of the balance by comparing the number of atoms on either side of the equation.
Step 7:
Since each type of atom is balanced on both sides, the equation is balanced. Let us now mention the physical state of each of the reactants and products.
The gaseous, liquid, aqueous and solid states of reactants and products are represented by the notations (g), (l), (aq) and (s), respectively. The word aqueous (aq) is written if the reactant or product is present as a solution in water.
3 Fe (s) + 4 H
2
O (g) → Fe
3
O
4
(s) + 4 H
2
(g)
Note that the symbol (g) is used with H
2
O to indicate that in this reaction water is used in the form of steam.

balanced chemical equation

18.Write the balanced equation for the following chemical reactions:
Hydrogen + Chlorine → Hydrogen chloride
Barium chloride + Aluminum sulphate → Barium sulphate + Aluminum chloride
Sodium + Water → Sodium hydroxide + Hydrogen.
Answer:
H
2
(g) + Cl
2
(g) → 2 HCl (g)
3 BaCl
2
(aq) + Al
2
(SO
4
)
3
(aq) → 3 BaSO
4
(s) + 2 AlCl
3
(aq)
2 Na (s) + 2 H
2
O (l) → 2 NaOH (aq) + H
2
(g).

balanced equation

Check here-SSLC-Karnataka State Science Important Questions with Answer (part 2)

19.Write balanced chemical equations with symbols for the following reactions:
Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Answer:
1. Barium chloride + Sodium sulphate → Barium sulphate + Sodium chloride
BaCl
2
(aq) + Na
2
SO
4
(aq) → BaSO
4
(s) + 2 NaCl (aq)
2. Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water
NaOH (aq) + HCl (aq) → NaCl (aq) + H
2

balanced chemical equations