chemistry adda: 9th chemistry Self-evaluation on Mole concept

**Sample Problem 1.**Calculate the number of mole in 52 g of Helium.**Solution.**We know that, Atomic mass of He = 4u

So, its molar mass = 4 g That is, 4 g of He contains 1 mole of He.

Or, 4 g of He = 1 mole of He

Or, 1 g of He = 1/4 mole of He

So, 52 grams of Helium =1/4 x 52 mole = 13 moles

Therefore, there are 13 moles in 52 g of He

**Sample Problem 2.**Calculate the number of moles for 12.044 X 10

^{23 }atoms of Helium.

Solution:

6.022 X 10

^{23 }atoms of Helium = 1 mole
1 atom of Helium =1/6.022 X 10

^{23 }mole
12.044 X 10

^{23 }atoms of Helium = [(1/6.022 X 10^{23}) x^{ }12.044 X 10^{23 }]moles
[ You may use ---- Number of moles = (given numbers of particles /Avogadro number)]

**Sample Problem 3.**How many moles are there in 5 grams of calcium?

**Sample Problem 4.**How many moles there in 12.044 X 10

^{23}atoms of phosphorous?

**Sample Problem 5.**Calculate the mass of 0.5 mole of Nitrogen atoms.

**Solution.**We know that, Molar mass of of Nitrogen atoms 14 g

The mass of 1 mole of Nitrogen atoms = 14 g

The mass of 0.5 mole of Nitrogen atoms = 14x 0.5 g = 7 g

Alternate method,

Mass = Number of moles X Molar mass

Or, = 0.5 X 14 = 7 g

Therefore, mass of 0.5 mole of N atoms is 7 grams.

**Sample Problem 6.**What is the mass of 3.011 X 10

^{23}number of Nitrogen atoms?

**Solution.**We know that, Molar mass of of Nitrogen atoms 14 g

The mass of 6.022 X 10

^{23 }number of Nitrogen atoms= 14 g^{}
The mass of 3.011 X 10

^{23}number of Nitrogen atoms = [(14g/6.022 X 10^{23 })x 3.011 X 10^{23}]g = 7 g**Sample Problem 7.**Calculate the number of particles in each of the following:

(i) 0.1 mole of Carbon atoms

(ii) 46 grams of Sodium atoms.

**Sample Problem 8**What is the mass of 4 moles of Aluminum atoms?

Determine the number of iron atoms in a piece of iron weighing 2.8 grams.

**Sample Problem 9**If one mole of Carbon atoms weigh 12 grams, what is mass in grams of a single atom of Carbon?

**Sample Problem 10.**Calculate the mass of 0.5 mole of N2 gas.

**Sample Problem 11.**Convert 12.044 X 10

^{22 }molecules of Sulphur dioxide into moles?

**Sample Problem 12.**In which case the number of Hydrogen atoms is more- 2 mol of HCl

or 1 mol of NH3?

**Sample Problem 13 .**An ornament of silver contains 20 gram silver. Calculate the moles of silver present.

**Sample Problem 14.**If 1 g sulphur dioxide contains x molecules, what will be the number

of molecules in 1 g of methane?

**Sample Problem 15.**Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.

**Sample Problem 16.**How many grams of neon will have the same number of atoms as 4 g of calcium?

**Sample Problem 17.**Calculate the number of iron atoms in a piece of iron weighing 2.8 grams.

**Sample Problem 18.**What is the mass of 3 moles of Zinc?

**Sample Problem 19 :**What is the ratio of molecules present in 6.6 grams of CO2 and 3.2 grams of SO

_{2}?

**Sample Problem 20.**If one gram of Sulphur contains x atoms, what will be the number of atoms in one gram of oxygen? (atomic mass of S = 32u)
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