Is this true? NaCl dissolving

  • Thread starter briton
  • Start date
  • #1
briton
30
0
considering the Na+ and Cl- in it's ionic lattice.

the formula, electrostatic force
F = Qq/(4.pi.e0.r^2)

where e0 is the permittivity of free space. However in water e0 is 80 times bigger, so
F= Qq/(4.pi.80e0.r^2), therefore electrostatic force between the ions is smaller, it simply dissolves and doesn't react.
 

Answers and Replies

  • #2
dextercioby
Science Advisor
Homework Helper
Insights Author
13,256
1,233
briton said:
considering the Na+ and Cl- in it's ionic lattice.

the formula, electrostatic force
F = Qq/(4.pi.e0.r^2)

where e0 is the permittivity of free space. However in water e0 is 80 times bigger, so
F= Qq/(4.pi.80e0.r^2), therefore electrostatic force between the ions is smaller, it simply dissolves and doesn't react.

The problem is ill posed.Water is not an "ether" (it's the weakest acid :tongue2: :tongue2: ),it's made up of molecules,just like sodium chloride is made up of atoms...The second formula u used cannot be put in that form,but in tha same form with the first,because,even in the presence of water molecules,the space between chlorine and sodium atom would still be vacuum,with the relative permitivity "+1".

Daniel.
 
  • #3
Andrew Mason
Science Advisor
Homework Helper
7,735
436
dextercioby said:
The problem is ill posed.Water is not an "ether" (it's the weakest acid :tongue2: :tongue2: ),it's made up of molecules,just like sodium chloride is made up of atoms...The second formula u used cannot be put in that form,but in tha same form with the first,because,even in the presence of water molecules,the space between chlorine and sodium atom would still be vacuum,with the relative permitivity "+1".
This is an interesting point. Water's permittivity is low because it is a polar molecule. In an electric field, polar molecules line up to reduce the electric field.

So, would one not have to know the distance between the Na+ and Cl- ions in solution? This would be a function of concentration. The electric potential between the molecules would be:

1. the coulomb potential or force between them (1/r^2), less
2. the opposing field from the water molecules between them

The latter is related to the number of water molecules between the Na+ and Cl-. When this number drops to 0, you will start to have precipitation.

So wouldn't permittivity of water be a factor?

AM
 

Suggested for: Is this true? NaCl dissolving

  • Last Post
Replies
5
Views
341
Replies
25
Views
893
  • Last Post
2
Replies
44
Views
800
  • Last Post
Replies
8
Views
380
Replies
15
Views
484
Replies
12
Views
577
Replies
12
Views
628
  • Last Post
Replies
27
Views
573
  • Last Post
Replies
16
Views
453
Top