why is it that only the first hydrogen bond in a polyproptic acid strong?
acid
Which of the following statements about ideal conditions for gases is considered untrue?
A. 1 mole of gas occupies 22.4 L at STP.
B. 2 moles of gas occupy 22.4 L at STP.
C. STP equals 1 atm at 237 K.
D. STP equals 101.3 kPa at 273 K.
1 mole of gas occupies 22.4 ltr at s.t.p
The strength of hydrogen bonds in polyprotic acids depends on several factors, including the acidity of the protons involved and the stability of the resulting ion. Polyprotic acids are substances that contain more than one ionizable proton, meaning they can donate multiple hydrogen ions (H+).
In the case of polyprotic acids, such as phosphoric acid (H3PO4) or sulfuric acid (H2SO4), the first hydrogen bond is generally strong because it involves the dissociation of the most acidic proton. Acidity refers to the tendency of a substance to donate a proton. The more acidic a proton, the more readily it dissociates (loses its hydrogen ion).
When polyprotic acids dissolve in water, the first proton is typically donated to a water molecule, forming a strong hydrogen bond. This bond is strong because the dissociation of the proton leads to the formation of a stable ion. For example, in the case of phosphoric acid (H3PO4), the first donated proton forms a phosphate anion (H2PO4-) by bonding with a water molecule (H2O). The formation of this ion is energetically favorable, resulting in a strong hydrogen bond.
However, as subsequent protons in a polyprotic acid dissociate, the acidity decreases because fewer stable ions can be formed. This leads to weaker hydrogen bonds for the subsequent dissociations. In the case of phosphoric acid, the second dissociation forms a less stable dihydrogen phosphate anion (HPO42-), and the third dissociation forms an even less stable hydrogen phosphate anion (PO43-). Therefore, the strength of the hydrogen bonds decreases with each successive dissociation.
In summary, the strength of hydrogen bonds in polyprotic acids depends on the acidity of the protons being donated and the stability of the resulting ions. The first hydrogen bond is typically the strongest because it involves the dissociation of the most acidic proton and leads to the formation of a more stable ion.