(I)how many atoms are present in 7g of lithium?

(Ii)How many atoms are present in 24g of carbon?

Calculate the number of moles in each of these substances

19g of fluorine, F2

22g of carbon dioxide, CO2

17g of hydroxide, OH- ions

Answer :

(i) The number of atoms present in 7 g of lithium are,

(ii) The number of atoms present in 7 g of lithium are,

(iii) The number of moles of is, 1 mole

The number of moles of is, 0.5 mole

The number of moles of is, 1 mole

Explanation :

Part (i) :

First we have to calculate the moles of lithium.

Molar mass of Li = 6.94 g/mole

Now we have to calculate the number of atoms present.

As, 1 mole of lithium contains number of atoms

So, 1.008 mole of lithium contains number of atoms

Thus, the number of atoms present in 7 g of lithium are,

Part (ii) :

First we have to calculate the moles of carbon.

Molar mass of C = 12 g/mole

Now we have to calculate the number of atoms present.

As, 1 mole of carbon contains number of atoms

So, 2 mole of carbon contains number of atoms

Thus, the number of atoms present in 7 g of lithium are,

Part (iii) :

To calculate the moles of :

Molar mass of = 38 g/mole

Thus, the number of moles of is, 1 mole

To calculate the moles of :

Molar mass of = 44 g/mole

Thus, the number of moles of is, 0.5 mole

To calculate the moles of ions :

Molar mass of = 17 g/mole

Thus, the number of moles of is, 1 mole