1. What is the H concentration in a urine sample that has a pH of 4? A) 0.1 B) 0
ID: 533234 • Letter: 1
Question
1. What is the H concentration in a urine sample that has a pH of 4? A) 0.1 B) 0.01 C) 0.001 D) 0.0001 E) None of the above 2. What pairs of atoms in bases are involved in hydrogen bonds? A) N-H and O-H B) N-H and S-H C) O-H and P-O D) All of the above. E) None of the above. 3. List atoms commonly found in biological molecules that are often hydrogen-bond acceptors. A) carbon B) oxygen C) nitrogen D) B and C E) All of the above. 4. What is the [A-y[HA] ratio when the weak acid is in a solution one pH unit above its pKa? A) 1:1 B) 1:10 C) 10:1 D) 2:1 E) None of the above. 5. Calculate the pH of a buffer solution made from 0.20 M HCrHyor and 0.050 M C2H302 that has a pKa 4.7 A) 2.8 B) 4.1 C) 5.3 D) 7.8 E) None of the above 6. What are the primary chemical components present in a phosphate buffer at pH 74? A) HPO, and PO B) H,PO and PO c) HPO4 2 and PO4 D) H2PO4 and HPO4 E) H3PO4 and HPO 2Explanation / Answer
1) Answer: D
Given; pH = 4
-log[H+] = 4
[H+] = 10^-4 = 0.0001 M
Therefore; Answer is D
2) Answer: D
A hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen (H) atom covalently bound to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F) experiences the electrostatic field of another highly electronegative atom nearby.
Since all the options contain the hydrogen attached to an electronegative atom, so all the possibilities form hydrogen bonds.
Therefore, Answer is: D
3) Answer: D
Nitrogen and oxygen are often formed hydrogen-bond acceptor in biological molecules.
4) Answer: C
Given that pH is one unit higher than pKa
Henderson–Hasselbalch equation:
pH = pKa + log[A-]/[HA]
pH-pKa = log[A-]/[HA]
1= log[A-]/[HA]
[A-]/[HA] = 10
[A-]/[HA] = 10:1 .
Therefore, answer is C
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