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(a) Ethyne C₂H₂
Molar Mass = 2 × 12 + 2 × 1
= 24 + 2
= 26 g.
(b) Molar mass of Sulphur molecule
= 8 × 32
= 256 g.
(c) Molar Mass of Phosphorus molecule
= 4 × 31
(Atomic mass of Phosphorus)
= 124 g.
(d) Molar mass of Hydrochloric acid
= HCl
= 1 + 35.5
= 36.5 g.
(e) Molar mass of HNO₃
= 1 + 14 + 3 × 16
= 15 + 48
= 63 gm.

100 grams of magnesium:

1 mole of Mg atom = 6.022 × 10²³ atoms

This means 24g of Mg has 6.022 × 10²³ atoms

Then 100 g contains:

Number of Mg atoms = \(\frac{Given\,mass}{Molar\,mass}\)x 6.022 x 10²³

Number of Mg atoms = \(\frac{100g}{24u}\)^x 6.022 x 10²³

Number of Mg atoms = 2.5 × 10²⁴ atoms

100 grams of aluminium:

1 mole of Al atom = 6.022 × 10²³ atoms

This means 27g of Al has 6.022 × 10²³ atoms

Then 100 g contains:

Number of AI atoms = \(\frac{Given\,mass}{Molar\,mass}\)x 6.022 x 10²³

Number of AI atoms = \(\frac{100g}{27u}\)^x 6.022 x 10²³

Number of AI atoms = 2.2 x 10²⁴

Thus, 100g of magnesium has more atoms.

(a) 32gm of oxygen means 1 mole

12gm oxygen means \(\frac{12}{32}\) mole

∴ 12g of oxygen gas = 0.375 mole

(b) 18 gm of water means = 1 mole

20 gm of water means \(\frac{20}{18}\) mole = 1.11 mole

(c) 22 g of carbon dioxide means 

\(\frac{22}{44}\) = 0.5 mole.

• The valency of oxide is 2 i.e., O^-2. 
• The formula of a metal oxide is given as MO. 
• Hence the valency of the given metal must be 2 i.e., M⁺². 
• Valency of chloride is 1 i.e., C^- . 
• Therefore according to criss -cross method, the formula of given metal chloride will be MCl₂ .

Correct answer: (b) 3 : 8

• Formula of calcium hydroxide is Ca(OH)₂. 
• From criss-cross method we know that the valency of calcium is 2 i.e., Ca⁺² and hydroxide is 1 i.e., OH^- .
•  Formula of zinc phosphate is Zn₃(PO₄)₂. 
• Valency of Zn is 2 i.e., Zn⁺² and valency of phosphate is 3 i.e., P\(O_4^{-3}\) . 
• Now the formula of calcium phosphate according to criss-cross method is Ca₃(PO₄)₂ .

The reaction in which the ions in the reactants are exchanged to form a precipitate is called double displacement reaction.

(a) Mass of 1 mole of nitrogen = 14g.
(b) Mass of 4 moles of Aluminium
= 4 × 27
= 108 g.
(c) Mass of 10 moles of Sodium sulphite
= 10 × [2 × 23 + 32 + 3 × 16]
= 10 × 126
= 1260 gm.

(a).Molecular mass of hydrogen sulphide (H₂S) 

= 2xH + 1xS = (2+32) u = 34u 

(b). Molecular mass of Carbon disulphide (CS₂) = 1xC + 2xS = (12+2 x 32) u = 76 u

Mass of oxygen atoms = number of molecules present 1g of hydrogen gas 

Number of molecules in 1g H₂ = 1/2 mole 

⇒ 1/2×6.022 × 10₂₃atoms 

⇒ 3.01 × 10²³ 

Thus, the mass possessed by certain number of oxygen atoms is 3.01 × 10²³

Given: 

Number of moles = 0.5 

Atomic mass of N = 14 u 

Molar mass of N = 14g/mol 

To calculate the mass, apply the formula:

Number of moles (n) = \(\frac{Molar\,(m)}{Molar\,mass\,(M)}\)

we can write:

Mass(m) = Number of moles (n) × Molar mass (M) 

Mass = 0.5 mol × 14g/mol 

Mass = 7g 

Thus, the mass of 0.5 mole of N atoms is 7g.

Given: At. Mass of AL = 27 u

Molar mass of aluminium oxide (Al₂O₃) = 2 × 27 + 3 × 16 = 54 + 48 = 102g

This means 102g of Al₂O₃ has 2 × 6.022 × 10²³ molecules

Then 0.051g contains:

Number of Al³⁺ ions = \(\frac{Given\,mass}{Molar\,mass}\)x 2 x 6.022 x 10²³

Number of Al³⁺ ions = \(\frac{0.051g}{102g}\)x 6.022 x 10²³

⇒ Number of Al³⁺ ions = 6.022 x 10²⁰

Thus.0.051 g of aluminium oxide contains 6.022 x 10²⁰ aluminium ions.

One mole of Sulphur (S) = 8 × 32

= 256 gm.

256 g of solid sulphur = 6.022 × 10²³ molecules.

= \(\frac{6.022\times 10^{23}}{256}\times 16\)

= 3.76 × 10²²

(Approximate)

The correct answer is (ii), (iii)

(a) Propanal

(a)  Benzene

(a) Both A and R are correct and R is the correct explanation of A

(c) Sand meyer reaction

(c) 1 – nitro butane and 2 – nitro butane

(a) C₆H₅CI + N₂

(d) Tautomerism

The mechanism is followed by the reaction of Ethyl bromide with ethanolic solution of potassium nitrite is S_N².

Phenol is formed when benzene diazonium chloride is boiled with water

(c) (i) and (iii)

(c) Nitro ethane

(a) Ethanol, hydrozylamine hydrochloride

(b) 3° nitro alkane

(a) Both A and R are correct and R is the correct explanation of A

(b) 2 – methyl – 2 – nitropropane

(a) Acetic acid

Example for nitro arenes is C₆H₅NO₂

108°  is the C – N – C bond angle of trimethylamine

Acetone is formed when 2- nitro propane is boiled with conc.HCI.

(b) Pyramidal

(d) A is wrong but R is correct

(b) 2 – methyl – 1 – nitro propane

1. Pyridoxine, vitamin B

2. alkaloids, biologically active amines

3. Nitrogen

4. Neurotransmitter

5. Histamine

6. tautomerism

7. Reddish brown 

8. Pseudo acids (or) Nitronic acids 

9. S_N2 

10. Methane

(a) Trimethyl amine

(d) Both (i) and (ii)

(CH₃)₃NH has the smallest pK value.

(c) Methyl amine

(c) Dimethyl amine

(c)  Aniline

(d) both aliphatic and aromatic 1° amine

(b) 2, 4 – dimethyl aniline

Primary and secondary amines are distinguished by HNO₂

(a) 1 Carbon atom less than amide

(a) iso cyanide

(b) 2° amine