Question

Calculate the mass, in kg, of each sample.

1.91×10²⁶ cadmium atoms.

4.68×10²⁷ nickel atoms

2.11×10²⁷ manganese atoms.

2.73×10²⁹ lithium atoms.

Express your answer with the appropriate units.

Answer 1

1.
molar mass of cadmium = 112.5 gm

number of moles = number of atoms/avogadro's number
    = (1.91*10^26) / (6.022*10^23)
   = 317.7 mol

mass = number of moles * molar mass
   = 317.7 *112.5 gm
   = 35682 gm
   = 35.682 Kg

2.
molar mass of Nickel = 58.5 gm

number of moles = number of atoms/avogadro's number
    = (4.68*10^27) / (6.022*10^23)
   = 7771.5 mol

mass = number of moles * molar mass
   = 7771.5 *58.5 gm
   = 454633 gm
   = 454.633 Kg

3.
molar mass of manganese = 55 gm

number of moles = number of atoms/avogadro's number
    = (11*10^27) / (6.022*10^23)
   = 18266.4 mol

mass = number of moles * molar mass
   = 18266.4 *55 gm
   = 1004650 gm
   = 1004.65 Kg

4.
molar mass of Lithium = 7 gm
number of moles = number of atoms/avogadro's number
    = (7.3*10^29) / (6.022*10^23)
   = 1212221.9 mol

mass = number of moles * molar mass
   = 1212221.9 *7 gm
   = 8485553 gm
   = 8486 Kg