Question

Calculate the number of atoms of copper represented by 127.08 g of copper. 1. 1.20 × 1024 atoms 2. 2.00 atoms 3. 1.30 × 1024 atoms 4. 2.16 atoms

Answer 1

Answer : The number of atoms of copper are
`1.20* 10^(24)`

Explanation :

First we have to calculate the moles of copper.

`\text{Moles of }Cu=\frac{\text{Mass of }Cu}{\text{Molar mass of }Cu}`

Mass of Cu = 127.08 g

Molar mass of Cu = 63.5 g/mole

`\text{Moles of }Cu=(127.08g)/(63.5g/mole)=2.00mole`

Now we have to calculate the number of atoms of copper.

As we know that, 1 mole of substance contains
`6.022* 10^(23)` number of atoms.

As, 1 mole of copper contains
`6.022* 10^(23)` number of copper atoms.

So, 2.00 mole of copper contains
`2.00* 6.022* 10^(23)=1.20* 10^(24)` number of copper atoms.

Therefore, the number of atoms of copper are
`1.20* 10^(24)`

Answer 2

Avagadros number states that 1 mol of any substance is made of 6.022 x 10²³ units.
1 mol of Cu is made of 6.022 x 10²³ atoms of Cu.
the molar mass of Cu is - 63.5 g/mol
63.5 g of Cu is made of 6.022 x 10²³ atoms of Cu
therefore 127.08 g of Cu contains - 6.022 x 10²³ atoms / 63.5 x 127.08
number of Cu atoms - 1.20 x 10²⁴ atoms of Cu
answer is 1) 1.20 x 10²⁴ atoms