Question

calculate the tota number of ions in 0.585g of sodium chloride.

Answer 1

Molecular Weight of NaCl= 23+35.5=58.5g per mole { as atomic mass of sodium = 23g per mole and atomic mass of chlorine atom is 35.5 g per mole }
Which means mass of 1 mole of NaCl = 58.5g 
Or 
58.5 g of NaCl contains = 1 mole of NaCl molecule
⇒1g of NaCl contains = (1/ 58.5) mole of NaCl molecules.
5.58g  of NaCl contains = (1×5.58/58.5) mole of NaCl molecules.
= 0.1 mole
Each molecule of NaCI contains one Na+ion and one Cl- ion = 2 ions

Total number of ions in 0.1 mole of NaCI = 2 x 0.1 = 0.2 moles
As 1 mole = 6.022 × 1023 particles
Therefore,
No. of ions present in 0.1 mole = 0.2 × 6.023 × 1023
= 1.2044 × 1023 ions

Answer 2

Molecular Weight of NaCl= 23+35.5=58.5g per mole { as atomic mass of sodium = 23g per mole and atomic mass of chlorine atom is 35.5 g per mole }
Which means mass of 1 mole of NaCl = 58.5g 
Or 
58.5 g of NaCl contains = 1 mole of NaCl molecule
⇒1g of NaCl contains = (1/ 58.5) mole of NaCl molecules.
5.58g  of NaCl contains = (1×5.58/58.5) mole of NaCl molecules.
= 0.1 mole
Each molecule of NaCI contains one Na+ion and one Cl- ion = 2 ions

Total number of ions in 0.1 mole of NaCI = 2 x 0.1 = 0.2 moles
As 1 mole = 6.022 × 1023 particles
Therefore,
No. of ions present in 0.1 mole = 0.2 × 6.023 × 1023
= 1.2044 × 1023 ions