1. Define ‘One mole’ of a substance.
2. Can ‘Avogadro constant’ be different for different substances? Explain.
3. Calculate the number of atoms present in 24g of Helium. (He = 4u)
4. Calculate the mass of atoms present in 0.5 moles of Nitrogen (N). (N=14u)
5. Calculate the no. of Moles in 36g of Water (H2O). (H=1u, O=16u)
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Answer: Number of atoms present in W g of a substance =
M
W
×N
a
.
Here, N
a
represents Avogadro's number. M represents the atomic mass of substance.
Number of atoms in 4 g He=
4
4
×N
a
=N
a
Number of atoms in 46 g of Na=
23
46
N
A
=2N
A
Number of atoms in 0.40 g of Ca=
40
0.4
N
A
=0.01N
A
Number of atoms in 12 g of He=
4
12
N
A
=3N
A
Hence, 12 g of helium has the maximum number of atoms.
Explanation:
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