how would you make up the following?

Question

a. 3.5 L of 0.75M NaCl

 

 

0.75 L of 22.5 M NaCl

 

 

 

Answer 1

(a) 3.5 L of 0.75M NaCl

 

V = volume of solution

 

M = molarity = (moles of solute) / (liters of solution) = 0.75 mols/L

 

n1  = moles of NaCl = VM = (3.5 L)(0.75 mols/L) = 2.625 mols

 

m1 = mass of NaCl

 

W1 = molecular weight of NaCl = 58.44 g/mol

 

Then m1 = n1*W1 = (2.625 mols)(58.44 g/mol) = 153.405 g

 

So to make 3.5 L of 0.75M NaCl, dissolve 153.405 g of NaCl in 3.5 L of H₂O.

 

(b)  0.75 L of 22.5M NaCl

 

Use same method, with different numbers.

 

n1 = VM = (0.75 L)(22.5 mols/L) = 16.875 mols

 

m1 = n1*W1 = ( 16.875 mols)(58.44 g/mol) = 986.175 g

 

So to make 0.75 L of 22.5M NaCl, dissolve 986.175 g of NaCl in 0.75 L of H₂O.

Answer 2

Hi Marissa,

NaCl's molecular mass is 58.44g/mol.

 

To make up 3.5L of 0.75M NaCl:

3.5L*(0.75M NaCl)= 2.625mol NaCl

2.625mol NaCl*(58.44g/mol)=153.405g NaCl

We need 153.405g NaCl

 

To make up 0.75L of 22.5M NaCl:

0.75L*(22.5M NaCl)=16.875mol NaCl

16.875mol NaCl*(58.44g/mol)=986.175g NaCl

We need 986.175g NaCl