Question

Q1. Calculate the number of atoms in 52g of He? *

(a) 6.022x10²³

(b) 3.13x10²⁵

(c) 7.83x10²⁴

(d) 6.022x10²⁴

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Answer 1

Explanation:

7.83 ×10^24

mole=given weight/molecular weight

n=52/4

n=13

no. of atom = mole ×Na

N= 13×6.022×10^23

so

N= 7.83×10 ^24

Answer 2

The number of atoms in 52g of He is 7.83×10²⁴ (option c)

To Find:

We need to calculate the number of atoms in 52g of He.

Solution:

At STP,

4 grams of He contains Avogadro Number ($N_{A}$) of atoms.

We know,

$N_{A}$ = 6.022 × 10²³

So, here we will use the unitary method.

Thus,

1 gm of He will contain $N_{A}/4$ no. of atoms.

52 gm of He will contain $\frac{N_{A}*52}{4}$ no. of atoms.

i.e,

52/4 × 6.022 × 10²³

= 7.83×10²⁴ no. of atoms

Thus, the number of atoms in 52g of He is 7.83×10²⁴.

Option C is correct.

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