# Number of HCl Equivalents in 100mL of pH 4 Solution

• Hydrous Caperilla
In summary: - dissociation does play a role, but is not always necessary for determining the concentration of a weak acid.
Hydrous Caperilla

## Homework Statement

Number of equivalents of HCL present in 100 ml of it's solution whose PH is 4

PH= -Log[H+][/B]

## The Attempt at a Solution

I used the above equation to find the concenteration of H+ and found it to be 10^-4 M.I am stuck after that. I searched the wiki and found a equivalent to be a substance which releases 1 mol of H+ in acid-base reaction but I don't find an acid base reaction here?[/B]

You need the volume of the solution in liters. If you know the molarity, (and yes, you calculated it correctly), how do you compute the number of moles? ## \\ ## HCl is assumed to ionize completely in solution. Likewise when mixed with a base, the HCl is assumed to react with 100% efficiency.

Hydrous Caperilla
Number of moles of HCl in the solution is then 10^-5 moles.

Do I have to assume to consider HCL as acid and water as base and proceed with this reaction

HCL(aq)-------->H+(aq)+Cl-(aq)

Hydrous Caperilla said:
Number of moles of HCl in the solution is then 10^-5 moles.

Do I have to assume to consider HCL as acid and water as base and proceed with this reaction

HCL(aq)-------->H+(aq)+Cl-(aq)
Not necessary, and that would really be incorrect (to assume it is reacting with water). What you are computing is the number of moles of ## H^+ ##, also called "equivalents" that are available to react with a basic (meaning "base") solution, such as NaOH. ##\\ ## And you computed it correctly. ## \\ ## (Such a reaction would neutralize the NaOH with the result being a NaCl (salt) solution which is neutral (neither acidic or basic). The ## OH^- ## would react with ## H ^+ ## to form ## H_2 O ## which is of course water).

Last edited:
Hydrous Caperilla
So regardless of the base,HCL will ionise completely and so we can calculate H+ ...right?

Hydrous Caperilla said:
So regardless of the base,HCL will ionise completely and so we can calculate H+ ...right?
That is correct.

Hydrous Caperilla
Thanx for the help

Hydrous Caperilla said:
So regardless of the base,HCL will ionise completely and so we can calculate H+ ...right?

When calculating number of equivalents dissociation is irrelevant in general. For a weak acid - like acetic - number of equivalents means "amount of H+ that can react" - not necessarily "dissociated".

In the case of your question 100% dissociation was an important factor in determining HCl concentration, other than that it didn't matter.

A fair point

## 1. What is the definition of HCl equivalents?

HCl equivalents refer to the amount of hydrochloric acid (HCl) present in a solution that is chemically equivalent to a specific amount of another acid or base.

## 2. How is the number of HCl equivalents determined in a solution?

The number of HCl equivalents can be calculated by multiplying the concentration of the acid or base in moles per liter (M) by the number of hydrogen or hydroxide ions that the acid or base can donate or accept, respectively.

## 3. How does pH affect the number of HCl equivalents in a solution?

The lower the pH of a solution, the higher the number of HCl equivalents present, as the concentration of hydrogen ions increases in acidic solutions.

## 4. Can the number of HCl equivalents change in a solution?

Yes, the number of HCl equivalents can change if the concentration of the acid or base in the solution is altered, or if the pH of the solution is changed through the addition of another acid or base.

## 5. What is the significance of knowing the number of HCl equivalents in a solution?

Knowing the number of HCl equivalents in a solution is important for understanding the strength and concentration of acids and bases, as well as for accurately performing chemical reactions and titrations in a laboratory setting.

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