Question

The atomic mass of calcium is 40u . What will be the number of calcium atoms atoms in 0.4u of calcium

Answer 1

Given:atomic mass of calcium is 40u.No. of moles =given weight/molecular weightNo. of Cu moles=0.4/40=1/00=0.01molesWe know that 1 mole of any substance contains 6.023 x 10²³ atoms/ molecules/ions1mole of Cu contains=6.023 x 10²³ atoms of Cu0.01 mole of Cu contains =6.023 x10²¹ atoms of calcium.
∴The no. of calcium atoms in 0.4 u of calcium are 6.023 x10²¹ atoms.

Answer 2

Weight of calcium is given = 0.4 g
Molar mass = 40 u

Number of moles = Weight / Molar mass
= 0.4 / 40
= 1/100
= 0.01
∴ No. of moles = 0.01

Now,
∵ Number of atoms = Avogadro number * Number of moles
= 6.022 * 10²³ * 0.01
= 6.022 * 10²³ * 10⁻²
= 6.022 * 10 ²³⁻²
= 6.022 * 10²¹

∴ The number of atoms in 0.4 grams of Calcium is 6.022 * 10²¹ .

Hope this helps you !!
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