Stoichiometry And Stoichiometric Calculations

The number of moles (n) is given by: . The number of molecules is given by , where is Avogadro's number.
For 1.0 g of H : Molar mass of H = 2.016 g/mol Moles of H mol
Number of molecules = 0.496
Let's check the options:
(1) 14 g of N : Molar mass of N = 28 g/mol Moles of N mol Number of molecules = 0.5
Thus, 14 g of N has approximately the same number of molecules as 1 g of H .

• A. 212 g of Na₂CO₃ (molar mass = 106 g/mol)

  • Moles = 212 g / 106 g/mol = 2 mol
  • Atoms per molecule = 2 (Na) + 1 (C) + 3 (O) = 6 atoms
  • Total "atoms" = 2 mol * 6 atoms/mol = 12

• B. 248 g of Na₂O (molar mass = 62 g/mol)

  • Moles = 248 g / 62 g/mol = 4 mol
  • Atoms per molecule = 2 (Na) + 1 (O) = 3 atoms
  • Total "atoms" = 4 mol * 3 atoms/mol = 12

• C. 240 g of NaOH (molar mass = 40 g/mol)

  • Moles = 240 g / 40 g/mol = 6 mol
  • Atoms per molecule = 1 (Na) + 1 (O) + 1 (H) = 3 atoms
  • Total "atoms" = 6 mol * 3 atoms/mol = 18

• D. 12 g of H₂ (molar mass = 2 g/mol)

  • Moles = 12 g / 2 g/mol = 6 mol
  • Atoms per molecule = 2 (H) = 2 atoms
  • Total "atoms" = 6 mol * 2 atoms/mol = 12

• E. 220 g of CO₂ (molar mass = 44 g/mol)

  • Moles = 220 g / 44 g/mol = 5 mol
  • Atoms per molecule = 1 (C) + 2 (O) = 3 atoms
  • Total "atoms" = 5 mol * 3 atoms/mol = 15

Now, we compare the total "atoms":

A = 12

B = 12

C = 18

D = 12

E = 15

A, B, and D have the same number of atoms (12).