Anonymous asked in Science & MathematicsChemistry · 1 decade ago

Why is HCl a stronger acid than HCOOH despite identical pH?

0.010M HCl = pH 2.0 ; 0.10 M HCOOH = pH 2.0

*Why is HCl a strong acid than HCOOH despite the fact that both these acid solutions have identical pH (pH 2.0). Explain.

*The pH of .01 M HCl is 1.0. The pH reading is theoretically impossible and therefore in error. Explain.

5 Answers

  • 1 decade ago
    Favorite Answer

    This relates to the dissociation of both acids. A stronger acid will dissociate (separate and let H+ go into solution) more. In this case HCl is higher. You can tell this by the molarity required to achieve the pH.

    Take pH to be -log [H] and assume 100% dissociation. Then [H] is equal to the molarity of the acid (.01 M). This gives us a pH of 2. Dissociation of HCl is not 100% but it is close.

    Take into account that pH is not truly -log [H], but really - log activity of H. Still -log [H] is a good approximation.This is not something most high school chemistry classes need you to know.

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  • rodent
    Lv 5
    1 decade ago

    1) The concentrations are different :-)

    2) HCl dissociates completely, so .01 M HCl theoretically contains .01 M H+ and the pH should be 2

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  • 4 years ago

    HCl is a strong acid. It completely disassociates in water. This means that in water it exits as H+ and Cl- and shows all the characteristics of strong acids. Weak acids do not completely disassociate in water. Acetic acid is a weak acid. CH3COOH. In water some of it exits as its ions CH3C00- and H+ but also some of it will stay as CH3COOH.

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  • Anonymous
    1 decade ago

    HCOOH is an organic acid, and organic acids are in our body (we wouldn't want really really strong acids burning holes through our body, now would we)? You can identify organic acids through 2 ways.

    1) It has a -COOH group.

    2) The number of oxygen is equal to or only 1 more than the number of hydrogen atoms.

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  • 1 decade ago

    1.HCl is an inorganic acid while HCOOH is an organic acid.inorganic acids dissociates more than organic acids,hence no.of H+ ions will be more in case of HCl than HCOOH.

    2.the molarity of these two acids are different.

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