Q: Write the balanced equation for the following chemical reactions. Barium chloride + Aluminium sulphate → Barium sulphate +Aluminium chloride

Solution The balanced chemical equation will be: 3BaCl2+Al2(SO4)3→3BaSO4+2AlCl3

Q: Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.

Water (H2O) contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test tubes is double of the amount collected in the other.

Question 1

Which of the statements about the reaction below are incorrect ?2 PbO(s) + C(s) --> 2Pb (s) + CO2​ (g)(a) Lead is getting reduced.(b) Carbon dioxide is getting oxidised.(c) Carbon is getting oxidised.(d) Lead oxide is getting reduced.

Accepted Answer

Oxidation is the gain of oxygen and reduction is the loss of oxygen. Lead is getting reduced due to gain of electrons and decrease in oxidation no.Similarly C is accepting O hence C is oxidising to CO2​.Hence, the correct option is B

Question 2

Write the balanced equation for the following chemical reactions.
Barium chloride + Aluminium sulphate → Barium sulphate +Aluminium chloride

Accepted Answer

Solution
The balanced chemical equation will be:
3BaCl2​+Al2​(SO4​)3​→3BaSO4​+2AlCl3​

Question 3

Write a balanced chemical equation with state symbols for the following reactions.Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Accepted Answer

SolutionThe balanced reaction is-NaOH(aq)+HCl(aq)→NaCl(aq)+H2​O(I)

Question 4

A solution of a substance ' X ' is used for whitewashing.
(i) Name the substance ' X ' and write its formula.
(ii) Write the reaction of the substance ' X ' named in (i) above with water.

Accepted Answer

(1) The substance X is calcium oxide whose solution is used in white washing CaO is also known as quick line.
Hence, has a chemical formula CaO.
(2) The reaction of quick lime (CaO) with water is written as shown below:
CaO(s)+H2​O(ℓ)⟶Ca(OH)2​(aq)
Quick lime slaked lime
(calcium oxide) (calcium hydroxide)
White washing in done with an aqueous suspension of calcium hydroxide (slaked lime).

Question 5

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Accepted Answer

Due to formation of Iron (II) sulphate which is of green colour, copper sulphate solution changes its colour.
(Blue) CuSO4​​​+Fe2+→(Green) FeSO4​​​+Cu2+

Question 6

Why should curd and sour substances not be kept in brass and copper vessels?

Accepted Answer

Curd and other sour substances are acidic in nature, if kept in brass or copper vessels, will react with the metal. The reaction will spoil the food and make unfit for human consumption or may cause food poisoning.

Question 7

Use Mendeleeve's Periodic Table to predict the formulae for the oxides of the following elements: K, C, Al, Si, Ba

Accepted Answer

Oxygen is a member of group VI. So, its valency is 2. Similarly, the valencies of all the elements listed can be predicted from their respective groups.(i) Potassium (K) is a member of group I having valency 1 . So, It forms oxide K2​O.(ii) Carbon (C) is a member of group IV having valency 4 . So, It forms oxide CO2​.(iii) Aluminium (AI) belongs to groups III having valency 3. So, It forms oxide Al2​O3​(iv) Silicon (Si) is present in group IV having valency 4. So, It forms oxide SiO2​.(v) Barium (Ba) belongs to group II having valency 2. So, It forms oxide BaO.

Question 8

Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Accepted Answer

Hydrogen gas is usually liberated when an acid reacts with a metal.

Take few pieces of zinc granules and add 5ml of dilute H2​SO4​ and shake it. The gas produced is passed into a soap solution. The bubbles of soap solution are formed. These soap bubbles contain hydrogen gas. The reaction occurs as follows:
H2​SO4​(aq)+Zn(s)→ZnSO4​(aq)+H2​(↑)
We can test the evolved hydrogen gas, as it burns with a pop sound when a candle is brought near the soap bubbles.

Question 9

Give an example of a double displacement reaction other than the one given in Activity 1.10.

Accepted Answer

Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride. two new compounds. Hence, it is a double displacement reaction.
Na2​CO3​(aq)+CaCl2​(aq)→CaCO3​(aq)+2NaCl(aq)

Question 10

Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.

Accepted Answer

Water (H2​O) contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test tubes is double of the amount collected in the other.

Question 11

Write the balanced equation for the following chemical reactions.Sodium + Water → Sodium hydroxide + Hydrogen

Accepted Answer

SolutionThe balanced chemical equation will be:2Na+2H2​O→2NaOH+H2​

Question 12

Write the balanced equation for the following chemical reactions.
Hydrogen + Chlorine → Hydrogen chloride

Accepted Answer

Balanced chemical equation: A balanced chemical equation is the representation of a chemical reaction in which the number of atoms of each element is the same on both the reactant and product sides.
Word equation to symbolic equation:
- In the given reaction, Hydrogen reacts with Chlorine to form Hydrogen chloride
- The chemical reaction can be represented as:
 Hydrogen H2​( g)​+ Chlorine Cl2​( g)​→ Hydrogen chloride HCl(g)​
Balancing the Chemical Equation:
Step 1: Write the number of atoms of each element
Element Reactant side Product Side
HCl​22​11​
- From the table, it is clear that the atoms of hydrogen and chlorine are not balanced.
Step 2: Balancing the unbalanced atoms
- In order to balance the equation, we will make the coefficient of HCl as 2 .
- Now the equation becomes
Element Reactant side Product Side
HCl​22​22​
Hence, the balanced chemical equation is H2​( g)+Cl2​( g)→2HCl(g)
Hydrogen Chlorine Hydrogen chloride

Question 13

Fe2​O3​+2Al ? Al2​O3​ +2Fe The above reaction is an example of a:.

Accepted Answer

The reaction is an example of displacement reaction.

Question 14

What are oxidising agents?

Accepted Answer

Some substances such as alkaline potassium permanganate and acidified potassium dichromate are capable of adding oxygen to others. These are known as oxidising agents.

Question 15

Identify the substances that are oxidised and the substances that are reduced in the following reactions.
(i) 4Na(s)+O2​ (g) →2Na2​O (s)
(ii) CuO (s) +H2​ (g) →Cu (s) +H2​O (l)

Accepted Answer

(i) Sodium ( Na ) is oxidised as it gains oxygen and oxygen gets reduced.
(ii) Copper oxide ( CuO) is reduced to copper (Cu) while hydrogen (H2​) gets oxidised to water (H2​O).

Question 16

Write a balanced chemical equation with state symbols for the following reactions.(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

Accepted Answer

SolutionThe balanced chemical equation is:BaCl2​(aq)+Na2​SO4​(aq)→BaSO4​( s)+2NaCl(aq)

Question 17

What happens when dilute hydrochloric acid is added to iron fillings?

Accepted Answer

When dilute HCl is added to iron fillings the reaction proceeds as:    2HCl+Fe→FeCl2​+H2​(g)In the reaction hydrogen gas and iron chloride are produced.

Question 18

What is a balanced chemical equation? Why should chemical equations be balanced?

Accepted Answer

A balanced chemical reaction is an equation that has equal numbers of each type of atom on both sides of the arrow. A chemical equation is a written symbolic representation of a chemical reaction. The reactant chemical(s) are given on the left-hand side and the product chemical(s) on the right-hand side. The law of conservation of mass states that atoms can neither be created nor destroyed in a chemical reaction, so the number of atoms that are present in the reactants has to balance the number of atoms that are present in the products.

Question 19

Translate the following statements into chemical equations and then balance them:(a) Hydrogen gas combines with nitrogen to form ammonia.(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.(c) Barium chloride reacts with aluium sulphate to give aluium chloride and a precipitate of barium sulphate.(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Accepted Answer

(a) Hydrogen gas combines with nitrogen to form ammonia.H2​(g)+N2​(g)→NH3​The balanced equation for this reaction can be written as:3H2​(g)+N2​(g)→2NH3​(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.H2​S(g)+O2​(g)→H2​O+SO2​The balanced equation for this reaction can be written as:2H2​S(g)+3O2​(g)→2H2​O+2SO2​(c) Barium chloride reacts with aluium sulphate to give aluium chloride and a precipitate of barium sulphate.BaCl2​+Al2​(SO4​)3​→AlCl3​+BaSO4​↓The balanced equation for this reaction can be written as:3BaCl2​+Al2​(SO4​)3​→2AlCl3​+3BaSO4​↓(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.K+H2​O→KOH+H2​The balanced equation for this reaction can be written as:2K+2H2​O→2KOH+H2​

Question 20

Balance the following chemical equations:(a) HNO3​+Ca(OH) 2​→Ca(NO3​) 2​+H2​O(b) NaOH+H2​SO4​→Na2​SO4​+H2​O(c) NaCl+AgNO3​→AgCl+NaNO3​(d) BaCl2​+H2​SO4​→BaSO4​+HCl

Accepted Answer

(a) 2HNO3​+Ca(OH)2​→Ca(NO3​)2​+2H2​O(b) 2NaOH+H2​SO4​→Na2​SO4​+2H2​O(c) NaCl+AgNO3​→AgCl+NaNO3​(d) BaCl2​+H2​SO4​→BaSO4​+2HCl

Chapter 1 : Chemical Reactions and Equations