Question

How many atoms are in 16.67g of Calcium Nitrate?

Answer 1

The number of atoms in calcium nitrate can easily be found by multiplying a given mole of Calcium Nitrate by Avogadro's number since each mole of a substance contains 6.03 × 10²³.

Now, mol of Ca(NO₃)₂ = mass of Ca(No₃)₂ ÷ molar mass of Ca(NO₃)₂
          mol of Ca = 16.67 g ÷ [(40 × 1) + (14 × 2) + (16 × 3 × 2) g/mol
          mol of Ca = 0.1016 mol

⇒ atoms of Ca(NO₃)₂ = 0.0812 mol × (6.02 × 10²³ atoms/mole)
                                    = 6.12 × 10²² atoms  

Answer 2

5.506x10^23 atoms First, determine the molar mass of Calcium Nitrate [ Ca(NO3)2 ]. Look up the atomic weights of the involved elements. Atomic weight calcium = 40.078 Atomic weight nitrogen = 14.0067 Atomic weight oxygen = 15.999 Molar mass Ca(NO3)2 = 40.078 + 2 * 14.0067 + 6 * 15.999 = 164.0854 g/mol Determine the number of moles of Ca(NO3)2. 16.67 g / 164.0854 g/mol = 0.101593439 mol Now multiply by the number of atoms in Ca(NO3)2 which is 9. So 9 * 0.101593439 = 0.914340947 Finally, multiply by avogadro's number. Giving: 0.914340947 * 6.0221409x10^23 = 5.50629001x10^23 Round the result to 4 significant figures, giving 5.506x10^23 atoms.