1) Which statement below is correct (true)?
a) Since HNO2 is a stronger acid than HF it must have a greater pKa.
b) Since HOCℓ is a stronger acid than HCN, then OCℓ– is a stronger base than CN–.
c) The dissociation (or ionization) of HOCℓ in water is HOCℓ + H2O º HCℓ + 2OH–.
d) The pH of a 0.10 M solution of acetic acid (Ka = 1.8 x 10-5) will be higher than the pH of a 0.10 M solution of formic acid (Ka = 1.8 x 10-4).
e) If the Kb for CH3NH2 is 5.0 x 10-4, the Ka for CH3NH3+ is 2.0 x 10-5.
My answer is that the pH of acetic acid will be higher than formic acid.
2)Which of the following is a Bronsted-Lowry base but not a Lewis base?
H2O, CN^-^, HSO4^-^, NH3, all choices are both B/L and Lewis base.
I know that H2O and NH3 are lewis base but I am not sure about CN^-^ and CO3^2-^. I think that CO3^2-^ is the answer that is not a lewis base.
Would you agree with my answers? Thank you for checking my answers.
#1 is ok.
#2. You don't have carbonate listed.
Oh Im sorry I missed that. CO3^2-^ is an answer listed. I was able to find that CN^-^ is a BL base but Im still not sure if it is a Lewis base. I do not think it is.
:C:::N:
CN^- is a B.L base because it can add a proton as H:C:::N:
and it has those lone pairs so it can donate electrons, too.
Ok so the only one im still not sure about is CO3^2-^. The -2 are lone pairs so I guess it is both Lewis and BL.
I think that's right.
1) Let's evaluate each statement to determine which one is correct:
a) The statement is incorrect. The pKa is a measure of acid strength, but it is inversely related to acid strength. A lower pKa indicates a stronger acid. Therefore, the correct answer cannot be a.
b) The statement is incorrect. The strength of a conjugate base cannot be determined solely based on the strength of the corresponding acid. The strength of a base is determined by its ability to accept a proton. Therefore, the correct answer cannot be b.
c) The statement is incorrect. The dissociation of HOCℓ in water should result in the formation of Hℓ and OH–, not HCℓ and OH–. Therefore, the correct answer cannot be c.
d) The statement is correct. The pH of a solution depends on the concentration of H+ ions, which in turn depends on the acid dissociation constant (Ka). Acetic acid has a lower Ka value than formic acid, indicating weaker acidity. Therefore, acetic acid will have a higher pH than formic acid. Thus, the answer could be d.
e) The statement is incorrect. The Kb and Ka values for a conjugate acid-base pair are related by the equation Ka x Kb = Kw (water dissociation constant). However, the given Ka and Kb values are not related in this way. Therefore, the correct answer cannot be e.
Based on the analysis, it seems that option d) is the correct statement.
2) A Lewis base is a compound or ion that donates an electron pair, while a Brønsted-Lowry base is a substance that accepts a proton (H+ ion). Let's evaluate the options to find the Bronsted-Lowry base that is not a Lewis base:
- H2O: This is both a Lewis base (donates a lone pair of electrons) and a Brønsted-Lowry base (accepts protons).
- CN^-: This is a Lewis base (donates a lone pair of electrons) and a Brønsted-Lowry base (accepts protons).
- HSO4^-: This is a Lewis base (donates a lone pair of electrons) and a Brønsted-Lowry base (accepts protons).
- NH3: This is both a Lewis base (donates a lone pair of electrons) and a Brønsted-Lowry base (accepts protons).
From the given options, all choices are both Brønsted-Lowry bases and Lewis bases. Therefore, the answer is actually that "all choices are both Brønsted-Lowry bases and Lewis bases."
It appears that your answer for the first question is correct, but the answer for the second question is different.