Question

Determine the number of atoms in each sample: 62.1 g titanium, Ti; 9.24 g neon, Ne; and 879 g lead, Pb

Answer 1

Q1)
Avagadros number states that 1 mol of any substance is made of 6.022 x10^23 units
In this case ,these units are atoms making up 1 mol of elements
Molar mass of Ti - 47.8 g/mol
since 1 mol contains 6.022 x10^23 atoms of Ti
Then 47.8 g contains 6.022 x10^23 Ti atoms
Then 62.1 g contains - 6.022 x 10^23 x (62.1/47.8) atoms of Ti
Therefore number of Ti atoms in 62.1 g are 7.82 x 10^23 atoms of Ti

Q2)
The molar mass of Ne is 20.2 g/mol
1 mol of Ne consists of 6.022 x 10^23 atoms of Ne
Therefore 20.2 g consists of 6.022 x 10^23 atoms of Ne
Then if 20.2 g have 6.022 x 10^23 atoms of Ne
Then 9.24 g of Ne are made of -
6.022 x 10^23 x (9.24/20.2 ) atoms of Ne
Therefore in 9.24 g of Ne there are 2.75 x 10^23 atoms of Ne

Q3)
The molar mass of Pb is 207.2 g/mol
Since 1 mol of Pb contains 6.022 x 10^23 atoms of Pb
And 1 mol has a mass of 207.2 g
Then 207.2 g of Pb consists of 6.022 x 10^23 atoms of Pb
Therefore 879 g of Pb has - 6.022 x 10^23 x (879/207.2) atoms of Pb
Number of Pb atoms in 879 g are 2.55 x 10^24 atoms of Pb

Answer 2

Answers:

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

Step-by-step 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