Question

The number of oxygen atoms in 24.9 g of CuSO4.5H2O is (molar mass of Cu = 63 g mol–1) (A) 2.41 × 1024 (B) 3.01× 1024 (C) 5.42 × 1023 (D) 5.42 × 1024​

Answer 1

Answer:-

option (a) 2.41 × 1024

soln:-

The number of oxygen atoms in 24.9 g of CuSO4.5H2O is 2.41 × 1024

Answer 2

Concept:

The number of moles can be defined as the ratio of a given mass to the mola mass of the compound.

n = m/mol

where n is the number of moles, mol is the molar mass and m is the given mass.

Given:

Mass of the compound CuSO₄.5H₂O = 24.9 g

Find:

The number of oxygen atoms present in the given mass.

Solution:

The molar mass of this compound,

CuSO₄. 5H₂O = (1 × 63) + (1 × 32) + (10 × 1) + (9 × 16)

= 63 + 32 + 10 + 144 = 249 grams

n = m/mol = 24.9/249

n = 0.1 moles

One mole contains 9 oxygen atoms,

So,  number of moles of oxygen atoms = 0.1 × 9 = 0.9 moles

1 mole contains 6.022 × 10²³ atoms.

Number of oxygen atoms = 0.9 × 6.022 × 10²³

N = 5.4198  × 10²³  atoms

N = 5.42 × 10²³  atoms

Hence, the total number of oxygen atoms in 24.9 g of CuSO₄.5H₂O is 5.42 × 10²³  atoms. Hence, the correct option is (c) 5.42 × 10²³.

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