Question

For the given elements, calculate the number of atoms in 1.00 gram of that element.

How many atoms of magnesium are in 1.00 gram? How many atoms of iron are in 1.00 gram? How many atoms of argon are in 1.00 gram?

Answer 1

1)

Molar mass of Mg = 24.31 g/mol

mass(Mg)= 1.00 g

number of mol of Mg,

n = mass/molar mass

=(1.0 g)/(24.31 g/mol)

= 0.0411 mol

number of atoms = number of mol * Avogadro’s number

number of atoms = 0.0411 * 6.022*10^23 atoms

number of atoms = 2.48*10^22 atoms

2)

Molar mass of Fe= 55.85 g/mol

mass(Fe)= 1.00 g

number of mol of Fe,

n = mass/molar mass

=(1.0 g)/(55.85 g/mol)

= 0.0179 mol

number of atoms = number of mol * Avogadro’s number

number of atoms = 0.0179 * 6.022*10^23 atoms

number of atoms = 1.08*10^22 atoms

3)

Molar mass of Ar = 39.95 g/mol

mass(Ar)= 1.00 g

number of mol of Ar,

n = mass/molar mass

=(1.0 g)/(39.95 g/mol)

= 0.0250 mol

number of atoms = number of mol * Avogadro’s number

number of atoms = 0.0250 * 6.022*10^23 atoms

number of atoms = 1.51*10^22 atoms