Question

Find the formula mass of NaCl and KCl.​

Answer 1

Answer:

Hint: The amount of 

NaClNaCl

 and 

KClKCl

 dissolved in a solution is equal. But they both have different molar mass. We will find the number of moles of each solution separately. Then we will find the molarity of each solution by assuming a fixed volume of solution. Thus we get the molarity of each solution respectively.

Formula Used:

Molarity = moles of solutevolume of solutionMolarity = moles of solutevolume of solution

Complete answer:

Since the weight of 

NaClNaCl

 and 

KClKCl

 dissolved in solution are equal, therefore we cannot find the molarity of these solutions separately. We will assume this equal weight is equal to the molecular mass of the solute 

NaClNaCl

. The molecular mass of 

NaClNaCl

 can be found as,

Molecular mass of 

NaCl = 23 + 35.5 gNaCl = 23 + 35.5 g

Molecular mass of 

NaCl = 58.5 gNaCl = 58.5 g

 which is now the equal weight of solute. Therefore we can say that for each solute the given mass is 

 58.5 g 58.5 g

. Now we will calculate molarity for each solute for one litre of solution.

Molarity of 

NaClNaCl

Given mass 

 = 58.5 g = 58.5 g

Molar mass 

 = 58.5 g = 58.5 g

Number of moles 

 = 58

Answer 2

Molecular weight of NaCl = 58.5 $gm / mol$; Molecular weight of KCl =  74.5 $gm/ mol$.

Explanation:

Sodium and Potassium are both alkali metals. They have 1 electron in the outer shell.

The molecular weight of Na: 23 $gm/ mol$

The molecular weight of K: 39 $gm / mol$

The molecular weight of Cl: 35.5 $gm/ mol$

Molecular weight of NaCl = Mol. wt of Na + Mol. wt of Cl

Molecular weight of NaCl = 23 + 35.5

Molecular weight of NaCl = 58.5 $gm / mol$

Molecular weight of KCl = Mol. wt of K + Mol. wt of Cl

Molecular weight of KCl = 39 + 35.5

Molecular weight of KCl =  74.5 $gm/ mol$