Question: You want to determine the cell density of a liquid bacterial culture so you perform a serial dilution. You inoculate TSA plates with 100 µl aliquots from dilution tubes. After incubation, you count the colonies on each plate and obtain the results listed below. Which plate should be chosen to calculate the original cell density (OCD)?

Answer Options:
Plate A: TNTC
Plate B: 360 colonies
Plate C: 60 colonies
Plate D: 10 colonies

Answer: Plate C: 60 colonies

Question: What is the molecular shape around the phosphorus atom in PH3?

Answer Options:
Linear
Bent
Trigonal planar
Tetrahedral
Trigonal pyramidal

Answer: Trigonal pyramidal

Question: Which measurement has the fewest number of significant figures?

Answer Options:
1.280 m
0.1280
0.001280
1280
All of the measurements have the same number of significant figures.

Answer: 1280

Question: What is the formula for the ionic compound formed when aluminum and sulfur combine?

Answer Options:
AlS
Al2S3
AlS3
Al2S
Al3S2

Answer: Al2S3

Question: How many total valence electrons does the polyatomic ion NH4+ possess?

Answer Options:
8
9
10
11

Answer: 8

Question: Approximately how many CFU would you expect to count if you plated 0.1 mL of a broth with a cell density of 3.50 x 10^2 CFU/mL?

Answer Options:
35 CFU
3.50 CFU
350 CFU
0.35 CFU

Answer: 35 CFU

Question: You have a culture with a cell density of 6.7 x 10^3 CFU/mL. What final dilution factor would give you countable plates from this culture?

Answer Options:
10^5
10^6
10^7
10^8
10^9

Answer: 10^6

Question: A syringe has a volume of 5.0 mL. What is this volume in deciliters?

Answer Options:
0.0005 dL
0.0050 dL
0.050 dL
0.50 dL
5.0 dL

Answer: 0.050 dL

Question: The purpose of performing serial dilutions and a standard plate count is to determine the _________.

Answer Options:
density of bacteria
identity of bacteria
source of bacteria

Answer: density of bacteria

Question: Select which of the following are examples of anions. Select all that apply.

Answer Options:
NH4+
Ni
Ca2+
Cl-
Ag+

Answer: Cl-

Question: If the density of a certain alcohol is 0.785 g/mL, what volume of the alcohol would have a mass of 75.0 g?

Answer Options:
95.5 mL
58.9 mL

Answer: 95.5 mL

Question: Carry out the following calculation and report the answer using the proper number of significant figures:
16.75 / 0.545

Answer Options:
31.0135 %
31.101 %
31.02 %
31.30 %
31.8 %

Answer: 30.73 %

Question: Approximately how many CFU would you expect to count if you plated 1.0 mL of a broth with a cell density of 3.52 x 10^2 CFU/mL?

Answer Options:
35 CFU
3.52 CFU
352 CFU
0.352 CFU

Answer: 352 CFU

Question: The number 0.0035880 expressed correctly using scientific notation is _________.

Answer Options:
0.0035889
3.5880 × 10^-3
3.5880 × 10^-2
3.5880 × 10^-4

Answer: 3.5880 × 10^-3

Question: Which particles are found in the atomic nucleus? Select all that apply.

Answer Options:
Protons
Electrons
Neutrons

Answer: Protons
Neutrons

Question: The symbol for the oxygen anion is O^2-. How many electrons does this anion have?

Answer Options:
6
8
10
Not enough information to determine.

Answer: 10