Acid Base Confusion: Solutions to Common Questions

In summary, the concentration of H+ ions in a weak acid that does not undergo complete dissociation can be approximated by mod H+=square root of Ka times C, where C is the initial concentration and Ka is the ionization constant. Similarly, for a weak base, the concentration of OH- ions can be approximated using Kb instead of Ka. However, this approximation is only valid within a certain range and cannot be used outside of that range.
  • #1
UchihaClan13
145
12
Please pay attention to the form of your posts, such short lines make it extremally difficult to read.
Hey all!
I have a silly doubt
In acids and bases
As you guys know
The concentration of H+ ions
For a weak acid
Which does not undergo
Complete dissociation
Is given by mod H+=square root of Ka times C
Where C is the initial concentration
Of the acid
And k is the ionization constant
In the same manner
For a weak base
The concentration of OH- ions
Is given in a similar manner
And ka is replaced by kb (assuming C remains constant for both of them)
Now assume that the acid and the base both are at 25 degrees centigrade
Thus kw=10^-14
Now multiplying mod H+
And OH-
We get 10^-14=10^-7 (square root of kw) times C
And thus C comes out to be 10^-7
Here is where the contradiction arises
If the concentration of the acid is less than 10^-7
And same for the base
Dissociation does occur
And their respective ph
Can be found
So why does C appear to be only 10^-7
Why a constant
Because concentration varies as per our will
We can add more solute in a solution or decrease the amount
If we want to!
Help is much appreciated
 
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  • #2
Guys
My doubt
Got cleared
I wasn't thinking properly
Thanks anyways
:)
 
  • #3
UchihaClan13 said:
For a weak acid
Which does not undergo
Complete dissociation
Is given by mod H+=square root of Ka times C

This is only an approximation, which holds under specific circumstances - you can't use it outside of the applicability range.

See http://www.chembuddy.com/?left=pH-calculation&right=pH-weak-acid-base for a discussion.
 

Related to Acid Base Confusion: Solutions to Common Questions

1. What is acid base confusion?

Acid base confusion refers to the confusion and misunderstanding surrounding the concepts of acids and bases, their properties, and their behaviors in solutions. It is a common issue in chemistry, especially for students and non-scientists.

2. What are acids and bases?

Acids are substances that donate protons (H+) when dissolved in water, while bases are substances that accept protons (H+) when dissolved in water. Acids are often described as sour, while bases are described as bitter or slippery. They have different properties and react differently in solutions.

3. What is the pH scale?

The pH scale is a measure of the acidity or basicity of a solution. It ranges from 0 to 14, with 0 being the most acidic, 14 being the most basic, and 7 being neutral. The scale is logarithmic, meaning that each number represents a 10-fold difference in acidity or basicity.

4. How do acids and bases interact in solutions?

Acids and bases can interact in different ways in solutions. When an acid and a base are mixed, they can neutralize each other and form a salt and water. This is known as a neutralization reaction. Acids can also react with water to produce hydronium ions (H3O+), while bases can react with water to produce hydroxide ions (OH-).

5. How can I differentiate between strong and weak acids and bases?

Strong acids and bases are substances that completely dissociate in water, meaning that all of the molecules split into ions. Examples include hydrochloric acid (HCl) and sodium hydroxide (NaOH). Weak acids and bases, on the other hand, only partially dissociate in water, meaning that only a small portion of the molecules split into ions. Examples include acetic acid (CH3COOH) and ammonia (NH3).

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