Calculate the number of molecules in 0.000400 grams of gaseous oxygen.

Question

Quizplus · Accepted Answer

1. Calculate the number of moles of oxygen: 
    n = m/M 
    where m = 0.000400 g (given), 
          M = molar mass of oxygen = 32 g/mol 
    n = 0.000400 g / 32 g/mol = 1.25 x 10^-5 mol.
2. Convert moles to molecules:
    Number of molecules = n * Avogadro's number (NA) 
    where NA = 6.02 x 10^23 molecules/mol 
    Number of molecules = (1.25 x 10^-5 mol) * (6.02 x 10^23 molecules/mol) = 7.52 x 10^18 molecules
    This is closest to 11eab077_f83c_755f_beed_a1f66b16362d_TB6421_11, which is choice D.

Calculate the Number of Molecules in 0