Question

Calculate the molecular masses of C2​H6​, C2H4, NH3​, CH3​OH, O2​

Answer 1

Required Answer :-

Molecular mass is the sum of the masses of the individual atoms.

(I) C₂H₆

Mass of carbon atom = 12

• Mass of C₂ = 2 × 12 = 24

Mass of Hydrogen atom = 1

• Mass of H₆ = 1 × 6 = 6

Now , Molecular mass of C₂H₆ is 24 + 6 = 30

Hence ,

• The molecular mass of C₂H₆ is 30

$\qquad$━━━━━━━━━━━━━━━━━

(II) C₂H₄

Mass of carbon atom = 12

• Mass of C₂ = 2 × 12 = 24

Mass of Hydrogen atom = 1

• Mass of H₄ = 1 × 4 = 4

Now , Molecular mass of C₂H₄ is 24 + 4 = 28

Hence ,

• The molecular mass of C₂H₆ is 28

$\qquad$━━━━━━━━━━━━━━━━━

(III) NH₃

Mass of Nitrogen atom (N) = 14

Mass of Hydrogen atom = 1

• Mass of H₃ = 1 × 3 = 3

Now , Molecular mass of NH₃ is 14 + 3 = 17

Hence ,

• The molecular mass of NH₃ is 17

$\qquad$━━━━━━━━━━━━━━━━━

(IV) CH₃OH

Mass of carbon atom (C) = 12

Mass of Hydrogen atom = 1

• Mass of H₃ = 1 × 3 = 3

Total mass of Hydrogen atoms in given compound = 3 + 1 = 4

Mass of Oxygen atom (O) = 16

Now , Molecular mass of CH₃OH is 12 + 4 + 16 = 32

Hence ,

• The molecular mass of CH₃OH is 32

$\qquad$━━━━━━━━━━━━━━━━━

(V) O₂

Mass of Oxygen atom = 16

• Mass of O₂ = 2 × 16 = 32

Hence , The molecular mass of O₂ is 32.

Answer 2

$\: \: \: \: \: \:{\large{\bold{\sf{\underbrace{\underline{Solutions}}}}}}$

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❶ Molecular mass of C₂H₆ is 30

❷ Molecular mass of C₂H₄ is 28

❸ Molecular mass of NH₃ is 17

❹ Molecular mass of CH₃OH is 32

❺ Molecular mass of O₂ is 32

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$\: \: \: \: \: \:{\large{\bold{\sf{\underbrace{\underline{Solution \: with \: explaintion}}}}}}$

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${\bold{\sf{Question \: 1}}}$ Calculate the molecular mass of C₂H₆

Here C is carbon atom and H is hydrogen atom.

➝ Mass of C is 12

➝ Mass of C₂ is 12 × 2

➝ Mass of C₂ is 24

➝ Mass of H is 1

➝ Mass of H₆ is 6 × 1

➝ Mass of H₆ is 6

➝ Molecular mass of C₂H₆ is 24 + 6 = 30

➝ Molecular mass of C₂H₆ is 30

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${\bold{\sf{Question \: 2}}}$ Calculate the molecular mass of C₂H₄

Here C is carbon atom and H is hydrogen atom.

➝ Mass of C is 12

➝ Mass of C₂ is 12 × 2

➝ Mass of C₂ is 24

➝ Mass of H is 1

➝ Mass of H₄ is 4 × 1

➝ Mass of H₄ is 4

➝ Molecular mass of C₂H₄ is 24 + 4 = 28

➝ Molecular mass of C₂H₄ is 28

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${\bold{\sf{Question \: 3}}}$ Calculate the molecular mass of NH₃

Here N is nitrogen atom and H is hydrogen atom.

➝ Mass of N is 14

➝ Mass of N is 14

➝ Mass of H is 1

➝ Mass of H₃ is 3 × 1

➝ Mass of H₃ is 3

➝ Molecular mass of NH₃ is 14 + 3 = 17

➝ Molecular mass of NH₃ is 17

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${\bold{\sf{Question \: 4}}}$ Calculate the molecular mass of CH₃OH

Here C is carbon atom , H is hydrogen atom , O is oxygen atom.

➝ Mass of C is 12

➝ Mass of H is 1

➝ Mass of H₃ is 3 × 1

➝ Mass of H₃ is 3

According to the question,

➝ Total mass of H atom in compound = 3 + 1 = 4

➝ Mass of O is 16

➝ Molecular mass of CH₃OH is 12 + 4 + 16 = 16 + 16 = 32

➝ Molecular mass of CH₃OH is 32

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${\bold{\sf{Question \: 5}}}$ Calculate the molecular mass of O₂

➝ Mass of O is 16

➝ Mass of O₂ is 16 × 2

➝ Mass of O₂ is 32

➝ Molecular mass of O₂ is 32

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