1. Which weak acid yields a buffer solution closest tp neutral pH when paired wi
ID: 999381 • Letter: 1
Question
1. Which weak acid yields a buffer solution closest tp neutral pH when paired with an equal concentration of its conjugate base? (A) acetic acid (K, 18x10 (C boric acid (K. 5Ax10 2. Which salt will form a neutral aqueous solution? (A) NaF (C) KBr 3. What is the pH of an aqueous solution of equal volumes of 060 M nitrous acid, HNO, and 0.30 M sodium nitrite, NaNO,? The K. of HNO, is 4A6x10 (A) 5.73 B) 4.12 (C 3.05 4. The pH of an aqueous 0.00796 M solution of HIO, is What is the K.of HIO? Do not assume that ionization is negligible with respect to the initial (A) 0.16 (B) 00076 (CO 0000037 0.21 According to Lewis theory,a Lewis acid is a(n) proton donor. B) electron-pair donor. (C) proton acceptor. (D) electron-pair acceptor. 6. Which acid is likely to result in the greatest percent ionization in aqueous solution? (A) 1 M HC H,Bro: K. 13x103 B) 1 M HCHO: K. 1 8x104 (C) I M HIO: K. 3.2x10 (D) 1 M Hss; K 1.0x10 1.0x10 7. A buffer solution consists of 0.100 mol of acetic acid (pKa 4.74) and 0.100 mol of sodium acetate in 1.00L of aqueous solution. How much will the pH increase if 0.010 mol of NaoH is added to the solution? (Assume that the volume remains constant.) (A) 0.040 (B) 0.087 (C) 0.15 D) 8. Which conjugate acid/base pair is norcorrect (A) H SO and SO. (B and (C HBr and Br (D HNO and 9. What is the pH of a 1AM aqueous hypochlor solution? The Ka for hypochlorous acid i 2 (A) 0.15 (B) 3.700 10. Which sketch best represents the titration of a diprotic acid with a strong base? (A) of base added Volume ofhe (C) 11. Identify and justify the Bronsted-Lowry acid in th reaction: NH HBr-NH Br (A NH, because it is a proton donor (B) HBr because it is a proton donor NH because it is a proton acceptor HBr because it is a proton acceptor 12. Which two elements form a compound with the stoichiometry X2Y,? (A) NaExplanation / Answer
Answers.
1. When concentrations of an acid and its conjugate base are equals, the pH of buffer system is equal to pKa of acid:
pH = pKa = -log(Ka)
pH (CH3COOH) = 4.74
pH (HCO3-) = 10.25
pH (H3BO3) = 9.26
pH (H2PO4-) = 7.20
Therefore, dihydrogen phosphate ion is the closest to pH (neutral = 7), that is 7.20.
Answer is D.
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2. In general, the fact that a salt which contains a metal alkaline ion and the conjugate base of a strong acid are considered neutrals with a pH close to 7.
NaF ==> Na+ + F-
KBr ==> K+ + Br-
These two reactions above does not accept or donate H+ ions as consequence is nuetral, in the other hand NH4 and Sr(C2H3O2)2 does accept or donate H+ ions.
Answers are A and C.
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3. Buffer systems can be show as salt/acid or conjugate base/acid, so;
pKa = -log(4.46x10-4) = 3.35
pH = pKa + log[salt]/[acid]
pH = 3.35 + log(0.30/0.60)
pH = 3.0496 = 3.05
Answer is C
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4. Knowing pH and solving the reaction we can obtain Ka as follows:
pH = -log[H+]
10-2.12 = 10-log[H+]
[H+] = 7.58x10-3 M
HIO3 ==> H+ + IO3-
0.00796-X x x
Ka = x2/(0.00796-x)
From reaction we know
[H+] = x
So,
Ka = (7.58x10-3)2/(0.00796-7.58x10-3)
Ka = 0.1512
From options the closest is 0.16, therefore; Answer is A.
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5. Yes, a Lewis acid is a sustance, able to accept a pair of electrons.
Answer is D.
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6. The more dilute the solution of acids the greater the percentage of ionization thereof. A logical and reasonable answer is that the H2S will be the highest percentage of ionization obtained, due to its diprotic condition, ionizes in two stages.
Answer is D.
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8. Question not clear please compare and choose the right one from the following:
H2SO4/HSO4-
H3O+/H2O
HBr/Br-
HNO3/NO3-
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11. Answer is C: NH3 because is a proton acceptor.
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12. From 3 options shown in the image, none of them forms a X2Y3 compound.. I guess is option D.
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