Question

Example 3.5 Determine the number of
particles in each of the following:
(i) 46 g of Na atoms (number from mass)
(ii) 8 g 0, molecules (number of molecules
from mass)
(iii) 0.1 mole of carbon atoms (number from
given moles)​

Answer 1

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a)46g of Na atom

atomic mass of Na=23u

Number of particles=Number of Moles x N

⇒(given weight/ Gram atomic weight) x 6.023 x 10²³

=(46/23)x 6.023 x 10²³

=2x 6.023 x 10²³

⇒12.046 x 10 ²³Na particles

∴46 g of Na contains 12.044 x 10 ²³

b)8g of O2 moles

molecular mass of O2=32u

No. Of molecules in O2 molecules=(8/32) x 6.022 x 10²³⇒0.25 x 6.023 x 10 ²³

⇒1.5055x 10 ²³ molecules

∴8g of O2 contains 1.5055x 10²³ molecules

c)0.1 moles of Carbon atom

1mole of carbon atom = 12 g of carbon contains 6.022 x 10²³ carbon atoms

0.1 moles of carbon contain =0.1 x 6.023 x 10²³

⇒ 6.023x10²² carbon atoms

∴0. mole contains 6.023x10²² carbon atoms

Answer 2

Explanation:

How many particles are there in 46 gram of Na atoms?

How many particles are there in 46 gram of Na atoms?Molar mass of sodium=23g/mol. The given mass of sodium is 46g. ∴ The number of particles present in 46g of Na atom is 12.046×1023.