What does molarity mean in case of weak electrolytes?

In summary, the conversation discussed the molarity of a solution containing 5 moles of acetic acid in 1 litre of water. The participants debated whether the molarity would be equal to 5 moles/volume of solution or if it would be determined by the number of moles of acetic acid dissolved in the solution. The expert summarizer clarified that molarity is defined as the number of moles well-mixed into solution, and in this case, the formal concentration of acetic acid would be 5 M. However, due to the dissociation of acetic acid, the equilibrium concentrations of HAcetate, Acetate-, and H+ would be different, resulting in a final molarity of 3
  • #1
AnkurGarg
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I am really confused about it.Suppose we add 5 moles of acetic acid in 1 litre of water..The molarity of solution will be -(5 moles)/volume of solution?Or it will be -(the number of moles of acetic acid dissociated/dissolved)/volume of solution
 
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  • #2
I believe molarity is defined as the number of moles dissolved or otherwise well mixed into solution. Vinegar and water are quite miscible so far I know, so it would be 5 moles/ liter.
 
  • #3
Molarity of what?

Formal concentration (also called analytical concentration) of acetic acid - 5 M.

Equilibrium concentrations of HAcetate, Acetate-, H+ will be different, you can estimate them to be approximately 4.990 M, 9.34×10-3 M and 9.34×10-3 M respectively. One thing you can be sure about is that [HAcetate] + [Acetate-] = 5 M (this is mass balance of acetic acid).
 
  • #4
No, molarity always is the quotient of moles per total volume, so 5 moles of acetic acid and one liter of water give a molarity less than 5 moles/l.
 
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  • #5
Good point.

Assuming 1 L of water and 5 moles of acetic acid final solution would be 3.96 M.
 
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1. What is molarity?

Molarity is a unit of concentration that measures the number of moles of a solute dissolved in a liter of solution. It is represented by the symbol "M" and is typically used in chemistry to describe the concentration of a solution.

2. How is molarity different for weak electrolytes?

In the case of weak electrolytes, the molarity will be different because not all of the solute molecules will dissociate into ions when dissolved in a solvent. This means that the concentration of ions in the solution will be lower than the molarity of the solute.

3. What does molarity tell us about a solution?

Molarity tells us the concentration of a solution, specifically the number of moles of solute per liter of solution. It can also be used to calculate other important properties of a solution, such as osmotic pressure and boiling point elevation.

4. How is molarity calculated for weak electrolytes?

Molarity for weak electrolytes is calculated by dividing the number of moles of solute by the total volume of the solution, including the volume of the undissociated solute molecules. This takes into account the fact that not all of the solute molecules will dissociate into ions in the solution.

5. Why is molarity important for studying weak electrolytes?

Molarity is important for studying weak electrolytes because it helps us understand the concentration of ions in a solution and how they affect properties like conductivity and pH. It also allows us to make comparisons and predictions about the behavior of different weak electrolytes in solution.

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