Calculate number of atoms in 120 g of calcium and 120 g of iron. Which

1.	Calculate number of atoms in 120 g of calcium and 120 g of iron. Which one has more number of atoms and how much is the difference? (Given atomic mass of calcium -40 u and iron = 56 u)
Answer» Molar mass of Calcium (Ca) = 40 g We know that the number of atoms in 1 mole of any element is given by the "Avagadro number " which is 6.023 × 10²³. So, number of moles in 120 gm of Ca = 120/40 = 3 So, number of atoms in 3 moles of Ca = 3 × 6.022 × 10²³ atoms. = 18.069 × 10²³ Molar mass of Iron (Fe) = 56 Number of moles in Fe = 120/56 = 2.14 Number of atoms in 2.14 moles of Fe = 2.14 × 6.023 × 10²³ = 12.89 ×10²³ 18.069 × 10²³ > 12.89 ×10²³ So, 120 g of Calcium has more atoms than 120 g of Iron. Difference = 18.069 ×10²³ - 12.89 × 10²³ = 5.179 ×10²³ atoms.

Calculate number of atoms in 120 g of calcium and 120 g of iron. Which one has more number of atoms and how much is the difference? (Given atomic mass of calcium -40 u and iron = 56 u)

Answer»

Molar mass of Calcium (Ca) = 40 g

We know that the number of atoms in 1 mole of any element is given by the "Avagadro number " which is 6.023 × 10²³.

So, number of moles in 120 gm of Ca = 120/40

= 3

So, number of atoms in 3 moles of Ca = 3 × 6.022 × 10²³ atoms.

= 18.069 × 10²³

Molar mass of Iron (Fe) = 56

Number of moles in Fe = 120/56

= 2.14

Number of atoms in 2.14 moles of Fe = 2.14 × 6.023 × 10²³

= 12.89 ×10²³

18.069 × 10²³ > 12.89 ×10²³

So, 120 g of Calcium has more atoms than 120 g of Iron.

Difference = 18.069 ×10²³ - 12.89 × 10²³

= 5.179 ×10²³ atoms.

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