Compare pH of HNO3 & HBr: Which is Stronger Acid?

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Discussion Overview

The discussion revolves around comparing the strength of two acids, HNO3 (nitric acid) and HBr (hydrobromic acid), focusing on their pH values and the parameters that define acid strength. Participants explore concepts related to pH, pKa, and acid dissociation, as well as the implications of concentration on acid strength.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions whether HNO3 can be a stronger acid than HBr based on their pH values, suggesting that lower pH indicates stronger acidity.
  • Another participant corrects the pH values provided, stating that the pH of 0.01M HNO3 is 2 and that of 10^-5M HBr is 5, arguing that these values cannot be used to compare acid strength directly.
  • Some participants propose that acid strength is defined by parameters such as pKa and dissociation constants rather than pH alone.
  • There is a discussion about the relevance of concentration in determining acid strength, with some participants suggesting that it must be considered alongside pH and pKa.
  • One participant mentions that while pKa indicates acid strength, pH is a property of the solution and not the acid itself, emphasizing the need for careful experimental design to compare acids.

Areas of Agreement / Disagreement

Participants express disagreement on the relationship between pH and acid strength, with some asserting that pH can be misleading without considering concentration and other factors. There is no consensus on a definitive method for comparing the strength of HNO3 and HBr based on the discussed parameters.

Contextual Notes

Limitations include the need for controlled conditions when comparing pH values of different acids, as well as the dependence on concentration and the specific definitions of acid strength being used.

omni
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which acid is more strong HNO3 or HBr?

i get the the pH for HNO3 is 5 and for HBr is 2 is it Possible if HNO3 is more strong acid so it must have the low pH than HBr yes?

thanks
 
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pH of 0.01M HNO3 is 2, and pH of 10-5M HBr is 5 - as these number are exactly opposite to what you have listed, they obviously can't be used to compare acid strength.

What parameters of acids do you know?
 
well 1x10^-5M for HNO3

and 1x10^-2 for HBr. but i think is it Possible Because HBr is a stronger acid than HNO3 yes?

thanks.
 
What defines acid strength? It is not pH, it is other parameter.

pH is not property of an acid, pH is a property of the solution.
 
Regarding other parameters of an acid: Besides HNO3 and H2SO4 causing low pH
in solution.Nitric acid is a very strong oxidizer and Sulphuric acid is a very strong
de-hydration acid.
 
Last edited:
conc. also has to be considered...
 
Hint: anyone here ever heard about acid dissociation?

--
 
i know that pka is What defines acid strength and also if the pH is more low so the acid is more strong no?

same for pka if it low so the acid is more strong truth?

thanks
 
Thats right the lower pKa the stronger the acid.
Also, Ka, the dissociation constant : (H+) (A-) /(HA)
Is more valid for the weaker acids since the stronger mineral acids are so highly
dissociated that Ka is not measurable.
 
  • #10
ok thank you. :-)
 
  • #11
omni said:
i know that pka is What defines acid strength and also if the pH is more low so the acid is more strong no?

Yes and no. Yes - pKa defines acid strength. No - pH is irrelevant, as it is not a property of acid, but property of a solution. In some cases it is possible to compare strength of acids by comparing pH of solutions, but it requires careful design of the experiment. In the simplest case you need solutions to have the same concentration, but in many cases that is not enough.
 

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