Question

A saline solution contains 40 g of common salt and 320 g of water. a) Calculate the number of moles of common salt present in the solution. b) number of molecules of atoms present in the solution.

Answer 1

Answer:

$\bigstar{\bold{Number\:of\:moles\:of\:NaCl\:=\:0.684\:moles}}$

$\bigstar{\bold{Number\:of\:molecules\:in\:solution\:=\:1.12\times10^{25}\:molecules}}$

Explanation:

Given:

• Mass of water (H₂O)= 320g
• Mass of common salt (NaCl) = 40g

To Find:

• Number of moles of common salt in the solution
• Number of molecules present in solution

Solution:

Number of moles of NaCl:

→ Molar mass of NaCl =23+35.5 = 58.5

→ Moles of NaCl = Given mass/Molar mass

→ Substitute the datas we get,

  Number of moles of NaCl = 40/58.5

  $\boxed{\bold{Number\:of\:moles\:of\:NaCl\:=\:0.684\:moles} }$

Number of atoms in solution:

→ Molar mass of H₂O = 2+16=18g

→ Number of moles of  H₂O = 320/18 = 17.78

→ Number of atoms = Number of moles×6.022×10²³

→ Number of atoms of NaCl = 0.684×6.022×10²³

  Number of atoms of NaCl = 4.12×10²³atoms

→ Number of atoms of H₂O= 17.78×6.022×10²³

   Number of atoms of H₂O= 107.07×10²³

→ Number of atoms in solution = No of atoms of NaCl+No of atoms of  H₂O

  Number of atoms in solution = 4.12×10²³+107.07×10²³

  Number of atoms in solution = 10²³(4.12+107.07)

  $\boxed{\bold{Number\:of\:molecules\:in\:solution\:=\:1.12\times10^{25}\:molecules} }$

Notes:

• Number of moles in a substance = Given mass of substance/Molar mass
• Number of molecules of a substance = Number of moles×6.022×10²³