NIOS Class 12 Chemistry Chapter 1 Atoms, Molecules and Chemical Arithmetic

NIOS Class 12 Chemistry Chapter 1 Atoms, Molecules and Chemical Arithmetic Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Chemistry Chapter 1 Atoms, Molecules and Chemical Arithmetic Notes in English and select need one. NIOS Class 12 Chemistry Solutions English Medium Download PDF. NIOS Study Material of Class 12 Chemistry Notes Paper Code: 313.

NIOS Class 12 Chemistry Chapter 1 Atoms, Molecules and Chemical Arithmetic

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Chemistry Notes, NIOS Senior Secondary Course Chemistry Solutions in English for All Chapter, You can practice these here.

Atoms, Molecules and Chemical Arithmetic

Chapter: 1

Module – I: Some Basic Concepts of Chemistry

INTEXT QUESTIONS 1.1

1. Chemistry plays a vital role in many areas of science and technology. What are those areas?

Ans: Health, medicine, energy, food, agriculture etc.

2. Who proposed the particulate nature of matter?

Ans: Leucippus and his student Democritus.

3. What is law of conservation of mass?

Ans: In every chemical reaction total masses of all the reactants is equal to the masses of all the products.

4. What is an atom?

Ans: An atom is extremely small particles of matter that retains its identity during chemical reaction.

5. What is a molecule?

Ans: Molecule is an aggregate of at least two atoms in a definite arrangement held together its chemical forces.

6. Why is the symbol of sodium Na?

Ans: It is derived from the Latin name of sodium i.e. Natrium.

7. How is an element different a form compound?

Ans: An elements comprises of atoms of one type only while a compound comprises atoms of two or more types combined in a simple but fixed ratio.

INTEXT QUESTIONS 1.2

1. Name the SI Unit of mass.

Ans: The SI unit of mass is kilogram.

2. What symbol will represent 1.0 × 10⁻⁶g?

Ans: The symbol μg represents 1.0 × 10⁻⁶g

3. Name the prefixes used for (i) 10² and (ii) 10⁻⁹

Ans: (i) h ( hecto).

(ii) n (nano).

4. What do the following symbols represent?

(i) Ms (ii) ms.

Ans: (i) Megasecond, 10⁶ s.

(ii) millisecond, 10⁻³s.

INTEXT QUESTIONS 1.3

1. A sample of nitrogen gas consists of 4.22 × 10²³ molecules of nitrogen. How many moles of nitrogen gas are there?

Ans: Moles of N₂ gas = (4.22 × 10²³ molecules) / (6.022 ×10²³  molecules mol⁻¹) = 0.70 mol .

2. In a metallic piece of magnesium, 8.46 × 10²⁴ atoms are present. Calculate the amount of magnesium in moles.

Ans: Amount of magnesium (moles) = (8.46 ×10²⁴ atoms) / (6.022 ×10²³ atoms mol⁻¹) = 14.05 mol.

3. Calculate the number of Cl₂ molecules and Cl atoms in 0.25 mol of Cl₂ gas.

Ans: No. of Cl₂ molecules in 0.25 mol Cl₂ = 0.25 × 6.022 × 10²³ molecules 

= 1.5055×10²³ molecules

Since each Cl₂ molecule has 2 Cl atoms, the number of Cl atoms = 2 × 1.5055 × 10²³ 

= 3.011×10²³ atoms.

INTEXT QUESTIONS 1.4

1. Calculate the molar mass of hydrogen chloride, HCl.

Ans: Molar mass of hydrogen chloride = molar mass of HCl

= 1 mol of H + 1 mol of Cl

= 1.0 g mol⁻¹ + 35.5 g mol⁻¹

= 36.5 g mol⁻¹.

2. Calculate the molar mass of argon atoms, given that the mass of single atom is 6.634 × 10⁻²⁶kg.

Ans: Molar mass of argon atoms = mass of 1 mol of argon

= mass of 6.022 × 10²³ atoms of argon.

= 6.634 × 10⁻²⁶ kg × 6.022 × 10²³ mol⁻¹

= 39.95 × 10⁻³kg mol⁻¹

= 39.95 g mol⁻¹.

3. Calculate the mass of 1.0 mol of potassium nitrate, KNO₃ (atomic masses : K = 39 amu; N = 14 amu, O = 16 amu).

Ans: Molar mass of KNO₃ = mass of 1 mol of K + mass of 1 mol of N + mass of 3 mol of O.

Since molar mass of an element is numerically equal to its atomic mass but has the units of g mol–1 in place of amu = 39.1 g + 14.0 g + 3 × 16.0 g

∴ Molar mass of KNO₃

= 39.1 g + 14.0 g + 48.0 g = 101.1 g mol⁻¹

4. The formula of sodium phosphate is Na₃PO₄. What is the mass of 0.146 mol of Na₃PO₄? (atomic masses : Na = 23.0 amu, P = 31.0 amu; O = 16.0 amu).

Ans: Mass of 1 mol of Na₃PO₄

= 3 × (mass of 1mol of Na) + mass of 1 mol

of P + 4 × (mass of 1mol of oxygen)

= 3 (23.0 g) + 31.0 g + 4(16.0) g

= 69.0 g + 31.0 g + 64.0 g = 164.0 g

∴ Mass of 0.146 mol of Na₃PO₄ = 0.146 × 164.0 g =  23.94 g.