SATHEE: Chapter 03 Atoms and Molecules Questions-04

Chapter 03 Atoms and Molecules Questions-04

Questions

1. Calculate the molecular masses of $H_{2}, O_{2}, C l_{2}, C O_{2}, C H_{4}, C_{2} H_{6}$ , $C_{2} H_{4}, N H_{3}, C H_{3} O H$ .

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Answer

(i) Molecular mass of $H 2$ (hydrogen)

$\begin{aligned} = Atomic mass of hydrogen \times 2 \\ = 1 \times 2 = 2 u \end{aligned}$

(ii) Molecular mass of $O 2$ (oxygen)

$=$ Atomic mass of oxygen $\times 2$

$= 16 \times 2 = 32 u$

(iii) Molecular mass of $C l 2$ (chlorine)

$\begin{aligned} = Atomic mass of chlorine \times 2 \\ = 35.5 \times 2 = 71 u \end{aligned}$

(iv) Molecular mass of $C O 2$ (carbon dioxide)

$\begin{aligned} = (Atomic mass of carbon \times 1) + (Atomic mass of oxygen \times 2) \\ = 12 + (16 \times 2) = 12 + 32 = 44 u \end{aligned}$

(v) Molecular mass of $C H 4$ (methane)

$= ($ Atomic mass of carbon $\times 1) + ($ Atomic mass of hydrogen $\times 4)$

$= 12 + (1 \times 4) = 12 + 4 = 16 u$ (vi) Molecular mass of $C 2 H 6$ (ethane)

$= ($ Atomic mass of carbon $\times 2) + ($ Atomic mass of hydrogen $\times 6)$

$= (12 \times 2) + (1 \times 6) = 24 + 6 = 30 u$

(vii) Molecular mass of $C 2 H 4$ (ethene)

$= ($ Atomic mass of carbon $\times 2) + ($ Atomic mass of hydrogen $\times 4)$

$= (12 \times 2) + (1 \times 4) = 24 + 4 = 28 u$

(viii) Molecular mass of $N H 3$ (ammonia)

$= ($ Atomic mass of nitrogen $\times 1) + ($ Atomic mass of hydrogen $\times 3)$

$= (14 \times 1) + (1 \times 3) = 14 + 3 = 17 u$

(ix) Molecular mass of $C H 3 O H$ (methanol or methyl alcohol)

$= ($ Atomic mass of carbon $\times 1) + ($ Atomic mass of hydrogen $\times 3) + ($ Atomic mass of oxygen $\times 1) + ($ Atomic mass of hydrogen $\times 1)$

$= 12 + 3 + 16 + 1 = 32 u$

2. Calculate the formula unit masses of $Z n O, N a_{2} O, K_{2} C O_{3}$ , given atomic masses of $Z n = 65 u$ , $N a = 23 u, K = 39 u, C = 12 u$ , and $O = 16 u$ .

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Answer

(i) Formula unit mass of $Z n O$ (zinc oxide) $=$ $65 + 16 = 81 u$

(ii) Formula unit mass of $N a 2 O$ (sodium oxide) $=$

$(23 \times 2) + (16 \times 1) = 46 + 16 = 62 u$

(iii) Formula unit mass of $K 2 C O 3$ (potassium carbonate) $=$

$(39 \times 2) + (12 \times 1) + (16 \times 3) = 78 + 12 + 48 = 138 u$

Chapter 03 Atoms and Molecules Questions-04

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Chapter 03 Atoms and Molecules Questions-04

Questions

Table of Contents

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Mentorship

NCERT Exercise Video Solution

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