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i. The mass of one mole of a substance (element/compound) in grams is called its molar mass.

ii. The molar mass of any element in grams is numerically equal to atomic mass of that element in u.

e.g.

iii. Similarly, molar mass of polyatomic molecule, in grams is numerically equal to its molecular mass or formula mass in u. 

e.g.

• Several naturally occurring elements exist as a mixture of two or more isotopes.
• Isotopes have different atomic masses. 
• The atomic mass of such an element is the average of atomic masses of its isotopes. 
• For this purpose, the atomic masses of isotopes and their relative percentage abundances are considered.

Hence,

The term average atomic mass is needed to express atomic mass of elements containing mixture of two or more isotopes.

The number of molecules present in 1 gm molecular weight of any substance. 

OR 

The number of atoms present in 1 gm atomic weight of any element. It is represented by the symbol N – 6.022 × 10²³.

The volume occupied by one mole of a gas at standard temperature (0°C) and pressure (1 atm) (STP) is called as molar volume of a gas. 

The molar volume of a gas at STP is 22.4 dm³.

(i) Empirical formula: The formula which gives the simple whole number ratio of the atoms of various elements present in one molecule of the compound is called empirical formula.

For example, empirical formula of hydrogen peroxide is HO. It represents that hydrogen and oxygen (i.e., H : O) are present in the ratio of 1 : 1 in hydrogen peroxide.

(ii) Molecular formula: The formula which gives the actual number of atoms of various elements present in one molecule of the compound is called molecular formula.

For example, the molecular formula of hydrogen. peroxide is H₂O₂ because one molecule of hydrogen peroxide contains two atoms of hydrogen and two atoms of oxygen.

Relation between Empirical and Molecular Formulae:

Molecular formula = n (Empirical formula)

where n is a simple whole number and may have values 1, 2, 3.... It is equal to

n = {Molecular mass}/{Empirical formula mass}

In many situations, an excess of one or more substance is available for chemical reaction. Some of these excess substances will therefore, be left over when the reaction is complete. The reaction stops immediately as soon as one of the reactants is totally consumed. Consider a chemical reaction given below initiated by passing a spark through a reaction vessel containing 10 mol of H₂ and 7 mol of O₂. Since 2 mol H₂ = 1 mol O₂, thus

                       2H₂ (g) + O₂ (g) → 2H₂O (g)

Moles before

reaction          10             7              0

Moles after

reaction           0              2              10

It is thus evident that the reaction stops only after consumption of 5 moles O₂ since no further amount of H₂ is left to react with unreacted O₂. The substance (here H₂) that is completely consumed in the reaction is called limiting reagent because it determines or limits, the amount of product. The other reactants present in excess are called as excess reagents.

(a) Molecular mass of NH₃ = (1 × Average atomic mass of N) + (3 × Average atomic mass of H)

= (1 × 14.0 u) +(3 × 1.0 u)

= 17 u

(b) Molecular mass of CH₃COOH = (2 × Average atomic mass of C) + (4 × Average atomic mass of H) + (2 × Average atomic mass of O)

= (2 × 12.0 u) + (4 × 1.0 u) + (2 × 16.0 u) 

= 60 u

(c). Molecular mass of C₂H₅OH = (2 × Average atomic mass of C) + (6 × Average atomic mass of H) + (1 × Average atomic mass of O) 

= (2 × 12.0 u) + (6 × 1.0 u) + (1 × 16.0 u) 

= 46 u

(i) {3.24 x 0.08666}/{5.006} = {0.2807784}/{5.006}

= 0.0561

(ii) 0.58 + 324.65 = 325.23

(iii) 1.78986 x 10³ = 1789.86

(iv) 943 x 0.00345 + 101 = 3.25 + 101 = 104.25

The SI unit for the amount of a substance is mole (mol).

A chemical equation which has an equal number of atoms of each element in the reactants and the products is called balanced chemical equation. 

Chemistry is the branch of science that studies the composition, properties and interaction of matter. 

(i) One mole of atoms = Gram atomic mass of the element

One mole of molecules = gram molecular mass

Mass of one atom = {Atomic mass}/{6.023 x 10²³}

(ii) Volume occupied by 1 mole of a gas at N.T.P. = 22.4 L

(iii) One mole of molecules = 6.023 x 10²³ molecules.

The number of particles in one mole is 6.0221367 × 10²³.

The mass of one mole of a substance is called its molar mass. 

The basic unit of mass in the SI system is kilogram (kg).

i. Centimetre Gram Second 

ii. Foot Pound Second 

iii. Metre (m) 

iv. Cd 

v. Kelvin (K) 

vi. Ampere (A)

6.022x10²³ molecules

It is defined as volume occupied by one mole of any substance.

Molar volume of a gas= 22.4 L at STP (273 K, 1 atm)

1 L atm × 10^-3 m³ /1L × 101.325Pa/atm =101.325 Pa m³ 

101.325 Pa m³ = 101.325(N/m² ) m³ =101.325 N m= 101.325 J

Chemical principles are important in diverse areas such as weather patterns, functioning of brain, operation of a computer, chemical industries, manufacturing , fertilizers, alkalis, acids, salts, dyes, polymers, drugs, soaps, detergents, metals, alloys, contribute in a big way to national economy.

• Mass is an inherent property of matter and is the measure of the quantity of matter of a body.
• The mass of a body does not vary with respect to its position.
• On the other hand, the weight of a body is a result of the mass and gravitational attraction
• Weight varies because the gravitational attraction of the earth for a body varies with the distance from the centre of the earth.

Hence,

The mass of a body is more fundamental property than its weight.

(B) 2.87x10 ^-11m

Sugar has close packing of constituent particles, have its own volume and shape therefore, it can be said to be solid whereas in water the constituent particles are not as closely packed as in solid. It has definite volume but not definite shape. Therefore it is a liquid. 

\(\because\) Mass = Volume x Density

Thus, mass of 1 liter of mercury (in gm)

= 1 L\(\Big[\frac{1000\,cm^3}{1\,L}\Big]\) [13.6 g cm^-3]

= 1.36 × 10⁴ g

Mass in Kilogram = 1.36 × 10⁴ g × \(\frac{1\,Kg}{100\,g}\) = 13.6 kg

The SI unit kilogram (kg) is related to gram (g) as 1 kg = 1000 g = 10³g.

[Note : ‘Gram’ is used for weighing small quantities of chemicals in the laboratories. Other commonly used quantity is ‘milligram’. 1 kg = 1000 g = 10⁶mg]

Molarity of a solution decreases on increasing temperature.

(i) It is the reactant which is entirely consumed when reaction goes to completion.

(ii) 2KClO₃(s) → 2KCl(s) + 3O₂(g)

Molecular weight of KClO₃ = 39 + 35.5 + 3 × 16

= 122.5

For 3 moles of O₂ we need

= 2 × 122.5 g of KClO₃

For 2.4 moles of O₂ we need

= \(\frac{2\times122.5}{3}\) x 2.4 = 196 g of KClO₃.

1 mole represent the amount of substance which contain Avagadro's number of particles.

Mass = Volume x density = 1000 cm³ × 13.6 g cm^-3 =13,600 g = 13.6 kg

Sugar is solid because it has definite volume and definite shape. Water is liquid because it has definite volume but not the definite shape.

It is the reactant which gets consumed first or limits the amount of product formed.

(ii) 3d⁵ shows highest magnetic moment. 

Correct Answer is: (C) -NH₂

Amino acids get their name from two "functional groups" or groups of atoms common to all these compounds. One of these groups is a carboxylic acid, the (C=O) OH on each amino acid. 

Equal volume of all gases and vapours under the same condition of temperature and pressure contains equal number of molecules.

M = n x \(\frac{1000}{Volume\,of\,solution\,in\,cm^3}\)

0.15 = n x \(\frac{1000}{27}\)

n = \(\frac{0.15\times27}{1000}\) = 0.00405 moles

Molar mass of water = 18.02 g

Mass % of hydrogen = \(\frac{Total\,mass\,of\,the\,elements\,in\,the\,compound}{Molar\,mass\,of\,the\,compound}\) x 100

=  \(\frac{2\times1.008}{18.02}\) x 100 = 11.18%

Mass % of oxygen = \(\frac{16.00}{18.02}\) x 100

= 88.79

Molecular Weight = 2 × V.D.

(a) Due to d-d transition

(b)Due to higher oxidation state of Mn₂O₇/Due to high polarizing power of Mn(VII).

Ions with incompletely filled d orbitals will be coloured. Due to d-d transition, Ti³⁺, V³⁺, Mn²⁺, Fe³⁺ and Co²⁺ are coloured. MnO₄^- is also coloured due to charge transfer. Only Sc³⁺ (3d⁰) is colourie.

μ = √4(4+2) = 4.90 B.M .

Cr²⁺(d⁴) changes to Cr³⁺ (d³) while Fe²⁺ (d⁶) changes to Fe³⁺ (d⁵). In aqueous medium d³ is more stable than d⁵.

(a) We know that,

Molarity = \(\frac{Number\,of\,moles\,of\,solute(HCl)}{volume\,of\,solution}\)

Number of moles of HCl

= \(\frac{Mass\,of\,the\,solute(HCl)}{Molecular\,mass\,of\,HCl}\) = \(\frac{38}{36.5}\)

Volume of solution:

38 g of HCl is present in 100 g of the solution

Volume of 100 g of the acid = \(\frac{Mass}{Density}\) = \(\frac{100\,g}{1.19\,g\,cm^{-3}}\) [\(\because\) 1mL = 1cm³]

= 84.033 ≈ 84.05 cm³

Molarity = \(\frac{\frac{38}{36.5}}{\frac{84.05}{1000}}\) ^{= 12.38 M}

(b) For monobasic acid

M₁V₁ = M₂V₂

12.38 M × V₁ = 10 M × 1000 mL

V₁ = \(\frac{10\,M\times1000\,mL}{12.38\,M}\)

= 807.754 ≈ 807.8 mL

Correct option is d. 3.58 kg

Correct option is c. 70 g

Correct option is a. 0.1 N