Respuesta :

Edufirst
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
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