Please include work on ones that appy 11. If the concentration of OHin water is
ID: 1017352 • Letter: P
Question
Please include work on ones that appy
11. If the concentration of OHin water is 3.5 x 10-8 , what is the pH?
A. 7.4 B. 3.2 C. 6.5 D. 9.1
12. If the pH of an aqueous solution is 8.2, what is the concentration of OH- ?
A. 1.58x10-6 B. 6.31x10-9 C. 4.16x10-8 D. 8.2x10-5
13. A solution with a OHconcentration of 9.2x10-10 is ________.
A. Neutral B. Basic C. Acidic D. pH 10
14. What is the predominate species for the H2PO4 - /HPO4 2- buffer at a pH of 8.5? Ka = 6.2x10-8
A. H3PO4 B. H2PO2- C. H2PO4 - D. HPO4 2-
15. Acidic solutions will turn a plant pigment molecule (blue litmus) from blue to __________.
A. green B. yellow C. black D. red
16. The CH3CH2CH2CH2- part in pentanoic acid is a ___________ group.
A. butyl B. propyl C. ethyl D. methyl
Explanation / Answer
11. If the concentration of OHin water is 3.5 x 10-8 , what is the pH?
pOH = -log 3.5 x 10-8
pOH = 7.46
pH = 14 - pOH
pH = 6.54
SO correct answer is
C. 6.5
12. If the pH of an aqueous solution is 8.2, what is the concentration of OH- ?
pOH = 14-pH
pOH = 14-8.2
pOH = 5.8
[OH-] = 10-pOH
[OH-] = 10-5.8
[OH-] = 1.58 x 10-6
Right answer is A. 1.58x10-6
13. A solution with a OHconcentration of 9.2x10-10 is ________.
pOH = -log OH
= - log 9.2x10-10
pOH = 9.03
pH = 14-pOH
pH = 4.96 so answer is
C. Acidic
14. What is the predominate species for the H2PO4 - /HPO4 2- buffer at a pH of 8.5? Ka = 6.2x10-8
pKa = -log Ka
pKa = - log 6.2x10-8
pKa = 7.21
pH = pKa + log base/acid
log base/acid > 0 means base is higher concentration
So answer is D. HPO4 2-
15. Acidic solutions will turn a plant pigment molecule (blue litmus) from blue to Red.
D. red
16. The CH3CH2CH2CH2- part in pentanoic acid is a butyl group.
A. butyl 4 carbon alkyl chain