pH

[Primarygun]

I have learnt something about pH value and wanna get some more of it. Anyone helps?

1.What does pH value refer to?

a. Amount of hydronium ions ionized by the acid per mole

b. Amount of hydronium ions ionized by the acid in the solution

c.Concentration of hydronium ions ionized by the acid molecule.

( Total amount of H3O+ ions/Total amount of molecules)

2. Will the concentration of an acid affect its pH value?

3. Will the molarity of an acid affect its pH value? If not, why we need to measure the pH value of ethanic acid and hydrochloric acid by means of electricity in the SAME MOLARLITY?

[jdurg]

1): pH is a measurement of the concentration of hydronium ions present in an aqueous solution of an acid. If it's not in water, it has no pH at the moment. (So technically speaking, 100% sulfuric acid would have no pH. Add some water and turn it into 98% sulfuric acid and it will have a very low pH).

 

2): The concentration of an acid definitely affects its pH value. pH is not an intrinsic property of a chemical. If you have 100 mL of a 1 molar HCl solution and 100 mL of a 10 molar HCl solution, the pH of the 10 molar solution will be noticeably lower. (Probably by a factor of 1 if my logarithimic math was done right in my brain).

 

3): Question 3 and Question 2 are exactly the same thing. Molarity, a term to describe concentration of a solute, plays a big role in the pH of a solution. The more moles of the acid you have, the more hydronium ions there will be and hence the lower the pH. A 1 molar solution of ethanoic acid has a different pH than a 1 molar solution of hydrochloric acid because HCl is a strong acid and fully dissociates in water while ethanoic acid is a weak acid and doesn't fully dissociate. It doesn't matter how many protons the acid can donate to the solution. What does matter is the number it actually DOES donate.

[Primarygun]

Thank you.

I want to ask one more question.

In which concentration, pH value is taken for a particular acid?

[pulkit]

Thank you.

I want to ask one more question.

In which concentration' date=' pH value is taken for a particular acid?[/quote']

 

pH is a measure of acid concentration.

So higher conc will give a lower pH (In most cases)

[budullewraagh]

i think that applies in all cases. does it not?

[Primarygun]

As the pH value of a particular solution varies with its concentration, at what concentration it is usually taken?

[kingjewel1]

pH is calculated at ALL concentrations: that is why we have a scale from 10^1 to 10^14 in log base ten.

 

Use pH of a strong acid (HCl or H2SO4) = -lg[H+]

in words: minus log base ten of hydrogen ion concentration.

Weak acids : pH =-lg sqrt([acid].Ka)

for weak acids all you need to know is their Ka value (their acid dissociation Konstant) and their concentration.

[Tetrahedrite]

Don't mean to be picky....pH is technically = -log activity (H3O+), not concentration. This only affects the value in super saline solutions etc