Question

$\Huge\rm{{Question}}$
What is the mass of –
(a) 1 mole of nitrogen atoms ?
(b) 4 moles of aluminium atoms ( Atomic mass of aluminium = 27) ? (c) 10 moles of sodium sulphite (Na, SO) ?

Class 9th Science Chapter 3 Atoms And molecules page no. 44.
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Answer 1

Answer:

(a)

• Number of moles present in 1 nitrogen atom = 1 mole

• Molar mass of nitrogen = 14 g/mol

$\longrightarrow\sf Mole = \dfrac{Given \: mass}{Molar \: mass}$

$\longrightarrow\sf n= \dfrac{ m}{M}$

$\longrightarrow\sf 1= \dfrac{ m}{14}$

$\longrightarrow\sf m = 1 \times 14$

$\longrightarrow \underline{ \underline{\sf m = 14 \: g}}$

(b)

• Number of moles present in aluminium atom = 4 moles

• Molar mass of aluminium = 27 g/mol

$\longrightarrow\sf n= \dfrac{ m}{M}$

$\longrightarrow\sf 4= \dfrac{ m}{27}$

$\longrightarrow\sf m = 4 \times 27$

$\longrightarrow \underline{ \underline{\sf m = 108 \: g}}$

(C)

• Number of moles present in sodium sulphite = 10 moles

•Molar mass of Na₂SO₃ :

=> molar mass of Na = 23 g/mol

=> molar mass of S = 32 g/mol

=> molar mass of = 16 g/mol

=> Number of atoms present in Na = 2

=> Number of atoms present in O = 3

$\longrightarrow\sf M = 23 \times 2 + 32 + 16 \times 3$

$\longrightarrow\sf M = 46 + 32 + 48$

$\longrightarrow \underline{ \underline{\sf M = 126 \: g/mol}}$

Mass :

$\longrightarrow\sf n= \dfrac{ m}{M}$

$\longrightarrow\sf 10= \dfrac{ m}{126}$

$\longrightarrow\sf m = 126 \times 10$

$\longrightarrow \underline{ \underline{\sf m = 1260 \: g}}$

Answer 2

Answer:

(a) 14 g

(b) 108 g

(c) 1260 g

Step-by-step explanation:

Asked questions :

What is the mass of –

(a)  1 mole of nitrogen atoms ?

(b) 4 moles of aluminium atoms ( Atomic mass of aluminium = 27) ?

(c) 10 moles of sodium sulphite (Na₂SO₃) ?

Given :

(a) Moles of nitrogen = 1

(b) Moles of aluminium = 4 ; Molecular weight of Aluminium = 27

(c) Moles of Sodium Sulphite = 10

Solution :

(a)

We know that,

$\boxed{\mathrm{Number\ of\ moles = \dfrac{Mass\ of\ element}{Molecular\ weight\ of\ element}}}$

Here, it is given that, moles of nitrogen is 1

we know that molecular weight of 1 mole of Nitrogen = 14g

From the formula,

Mass of element = Moles × Molecular weight

⇒ Mass of Nitrogen = 1 × 14

⇒ Mass of Nitrogen = 14g

_________________________

(b)

Here, it is given that, moles of aluminium is 4

we know that molecular weight of 1 mole of Aluminium = 27g

From the formula,

Mass of element = Moles × Molecular weight

⇒ Mass of aluminium = 4 × 27

⇒ Mass of aluminium = 108g

_________________________

(c)

Here, it is given that, moles of sodium sulphite is 10

First, let us know the molecular mass of sodium sulphite

The formula of Sodium Sulphite is Na₂SO₃

We have, 2 atoms of Sodium, 1 atom of Sulphur and 3 atoms of Oxygen in 1 mole of Sodium Sulphite

We know that,

Molecular mass of Sodium = 23 ; Sulphur = 32 ; Oxygen = 16

So, Molecular weight of Na₂SO₃ = (2 × Na) + (1 × S) + (3 × O)

⇒ (2 × 23) + (1 × 32) + (3 × 16)

⇒ 46 + 32 + 48

⇒ 126 g

∴ Molecular weight of 1 mole of Na₂SO₃ = 126 g

So, here we are asked to find mass of 10 moles of Na₂SO₃

From the formula,

Mass of element = Moles × Molecular weight

⇒ Mass of Sodium sulphite = 10 × 126

⇒ Mass of Sodium sulphite = 1260g

Hope it helps!!