Elements are ordered from left to right, increasing atomic number as they go. The periodic table allows us to find out and predict things about elements that haven’t been discovered yet!
We are given the base dissociation constant, Kb, for Pyridine (C5H5N) which is 1.4x10^-9. The acid dissociation constant, Ka for the Pyridium ion or the conjugate acid of Pyridine is to be determined. We know from our chemistry classes that:
Kw = Kb * Ka
where Kw is always equal to 1x10^-14
so, to solve for Ka of Pyridium ion, substitute Kb to the equation together with Kw and solve for Ka:
1x10^-14 = 1.4x10^-9 * Ka
solve for Ka
Ka = 7.14x10^-6
Therefore, the acid dissociation constant of Pyridinium ion is 7.14x10^-6.
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Amphiprotic compounds are able to both donate and accept a proton.
Amphiprotic compounds contain a hydrogen atom and lone pair of valence electron.
For example, HSO₃⁻ (hydrogen sulfate ion) is an amphiprotic compound.
Balanced chemical equation for reaction when HSO₃⁻ donate protons to water:
HSO₃⁻(aq) + H₂O(l) ⇄ SO₄²⁻(aq) + H₃O⁺(aq).
Ka = [SO₄²⁻] · [H₃O⁺] / [HSO₃⁻]
Balanced chemical equation for reaction when HSO₃⁻ accepts protons from water:
HSO₃⁻(aq) + H₂O(l) ⇄ H₂SO₄(aq) + OH⁻(aq).
Kb = [H₂SO₄] · [OH⁻] / [HSO₃⁻]
Water (H₂O), amino acids, hydrogen carbonate ions (HCO₃⁻) are examples of amphiprotic species.
Another example, water is an amphiprotic substance:
H₂O + HCl → H₃O⁺ + Cl⁻
H₂O + NH₃ → NH₄⁺ + OH⁻
More about amphiprotic compounds: brainly.com/question/3421406
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When it comes to physical changes like phase changes, there are two types of heat energy: sensible heat and latent heat. Sensible heat is the heat absorbed/released when you heat the substance but it doesn't change phase. An example would be heating lukewarm water. The substance is liquid all throughout. Latent heat, on the other hand, is the heat absorbed/released when there is a phase change. An example would be boiling water, because it changes liquid to vapor.
Hence, for freezing liquid, you use the latent heat, specifically the heat of fusion. The answer should be
2.5 g * (1 mol/18.02 g) * 6.03 kJ/mol = 0.84 kJ/mol
The answer is not in the choices. You only use Hvap if you boil water.
