Determine the number of atoms in each sample: 62.1 g titanium, ti; 9.24 g neon, ne; and 879 g lead, pb

Answers:

Ti: 5.49 × 10²²
Ne: 2.75 × 10²³
Pb: 2.55 × 10²⁴

Explanation:

You need to use the mass formula from the molar mass equation:

1) By definition: atomic mass = mass of 1 mole of atoms

⇒
                         mass in grams
atomic mass =
                         number of moles

Solving for number of moles:

                                   mass in grams
number of moles = 
                                    atomic mass

2) search for the atomics masses of the elements in a periodic table and compute the number of moles. This table shows you how:

element     atomic mass      mass in grams   number of moles
                     (g/mol)                   (given)

Ti                47.687               62.1                    62.1g/47.681g/mol = 0.0912 

Ne              20.180               9.24                    9.21g / 20.18g/mol = 0.456

Pb               207.2                879 g                  879g / 207.2g/mol = 4.24

3) use Avogadro's number to convert number of moles into number of atoms

Formula:
number of atoms = Avogadro's number × number of moles

number of atoms = 6.022 × 10 ²³ atoms/moles × number of moles

Answers:

element         number of atoms                     

Ti                    0.0912 × 6.022 × 10²³ =  5.49 × 10²²

Ne                  0.456 × 6.022 × 10²³ = 2.75 × 10²³

Pb                  4.24 × 6.022 × 10²³ = 2.55 × 10²⁴

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