Question

PLEASE give solution for Question 21-29

Answer 1

Given Mass = 0.09g

The molar mass of water is 18g/m

We know that,

Mass= moles × molar mass

Or, Moles = Mass/ Molar mass

or, Moles = 0.09/ 18

or, Moles = 0.005

Again,

1 mole of any particle contains 6.022 × 10^23

0.005 mole of any particle contains 6.022 × 10^23 × 0.005 or, 3.011 × 10^21
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2) The molecular mass of S8 is 256g/m


Mass = Moles × molar mass

or,Moles = Mass/ molar mass

or, Moles= 5.12 / 256

or, Moles = 0.02

0.02 moles of Sulfur are present.

Now,

The number of Sulfur molecules = Number of moles × Avogadro number

Or, The number of Sulfur molecules = 0.02 × 6.022 × 10^23 or, 1.204 × 10^22

The number of atoms in Sulfur = 1.50 × 10^ 23 × 8 or, 1.2 × 10^24
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3)The molar mass of Phosphorus = 124g/m

Mass = Moles × Molar mass

or, Moles = Mass /Molar mass

or, Molar mass = 100/124

or, Molar mass = 0.8

Number of moles = 6.022 × 10^23 × 0.8 or, 4.81 × 10^23
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5) 1 mole of carbon contains 12 g carbon.

12 g carbon has 6.022 × 10^23 carbon atoms

So, 10^-12 g carbon has 6.022 × 10^23/12 × 10^-12 or 5.02 × 10^10 carbon atoms.
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6) Given,

Density = 3 g/lit

Temperature = 273°c or, 546K

Pressure = 1140 mmHg or 1.5 atm

We know,

Density = Mass / Volume

3 = Mass / 1

or, Mass = 3 g

According to Ideal Gas law,

PV = nRT

or, PV = m/M RT [ as we know Mass= Moles × molar mass]

or, 1.5 × 1 = 3 /M × 0.082 × 546

or, 1.5 = 3/ M × 0.082 × 546

or, 1.5M = 134.3

or, M = 134.3/ 1.5

or, M= 89.5g/m

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6) Molecular Mass of Suger=342g/ m

Given,

the cost of 1000g suger [as 1kg =1000g] is 40

the cost of 342g suger is 40/ 1000× 342 or,₹ 13.68

So the cost per mole is ₹13.68
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7)I think the answer should be 2 g of Nitrogen weights the least.

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8)The Molecular Mass of Caustic Soda is 40g/m

40g NaOH contains 6.022×10^23 particles

4 g of NaOH contains 6.022× 10^23/40× 4 or, 6.02×10^22

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Hope it helps