Nokea
The cargo of uranium hexafluoride weighed kg and was contained in 30 drums, each containing L of UF . What is the density (g/mL) of uranium hexafluoride?
- A. 1.53 g/mL
- B. 5.11 g/mL
- C. 2.25 g/mL
- D. 0.196 g/mL
Correct Answer: C
Rationale: To find the density, we first calculate the total volume of uranium hexafluoride. Since each drum contains 15 L, the total volume is 30 drums * 15 L/drum = 450 L. Next, convert the mass from kg to g (1 kg = 1000 g). Density = mass/volume. Density = (mass in g) / (volume in mL). Since the mass is in g, we need to convert the volume from L to mL (1 L = 1000 mL). Density = (mass in g) / (volume in mL) = (mass in g) / (volume in L * 1000). Density = (mass in g) / (450 L * 1000) = (mass in g) / 450000 mL. Therefore, the density is the mass divided by 450000. The correct answer is C: 2.25 g/mL. Choice A is incorrect as it is too low
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On a new temperature scale (°Z), water boils at 0°Z and freezes at 0°Z. Calculate the normal human body temperature using this temperature scale. On the Celsius scale, normal human body temperature could typically be 1°C, and water boils at 0°C and freezes at 00°C.
- A. 2968°Z
- B. 12.4°Z C)
- C. 111°Z
Correct Answer: A
Rationale: To calculate normal human body temperature in °Z, we can use the formula: °Z = (°C + 100) / 2. Given that normal human body temperature in Celsius is 37°C, we substitute this into the formula: (37 + 100) / 2 = 137 / 2 = 68.5°Z. Therefore, the correct answer is A: 2968°Z, as it is the closest to 68.5°Z.
Summary of other choices:
B: 12.4°Z - This is too low, as human body temperature is higher.
C: 111°Z - This is too high, as it exceeds the calculated value of 68.5°Z.
You measure water in two containers: a 10-mL graduated cylinder with marks at every mL, and a 1-mL pipet marked at every 1 mL. If you have some water in each of the containers and add them together, to what decimal place could you report the total volume of water?
- A. 0.01 mL
- B. 0.1 mL
- C. 1 mL
- D. 10 mL
Correct Answer: C
Rationale: The correct answer is C: 1 mL. When adding volumes measured in different containers, you should report the result to the least precise measurement scale, which is the 1 mL pipet in this case. The graduated cylinder measures to the nearest mL, so the total volume should be rounded to the nearest whole mL. Reporting to a decimal place of 0.01 mL or 0.1 mL would imply a level of precision greater than what the equipment can provide. Choice D is incorrect as it exceeds the maximum volume capacity of the containers and is not relevant to the precision of the measurements.
We generally report a measurement by recording all of the certain digits plus uncertain digit(s).
- A. no
- B. one
- C. two
- D. three
Correct Answer: B
Rationale: Step 1: In measurement, certain digits are the numbers that are known for sure.
Step 2: Uncertain digits are the last digit that is estimated or measured.
Step 3: We record all the certain digits and one uncertain digit to indicate the precision of the measurement.
Step 4: Choice A is incorrect because we do include uncertain digit(s) in the measurement.
Step 5: Choice C and D are incorrect as including two or three uncertain digits would provide excessive precision beyond what is known for certain.
The amount of uncertainty in a measured quantity is determined by:
- A. both the skill of the observer and the limitations of the measuring instrument
- B. neither the skill of the observer nor the limitations of the measuring instrument
- C. the limitations of the measuring instrument only
- D. the skill of the observer only
Correct Answer: A
Rationale: The correct answer is A because the amount of uncertainty in a measured quantity is influenced by both the skill of the observer and the limitations of the measuring instrument. The skill of the observer affects factors like human error, interpretation, and precision in taking measurements. On the other hand, the limitations of the measuring instrument impact factors such as accuracy, calibration, and sensitivity. Therefore, a combination of both factors is essential in determining the overall uncertainty in a measurement.
Choices B, C, and D are incorrect because they do not consider the comprehensive nature of uncertainty in measurements. Choice B is incorrect as both the observer's skill and the instrument's limitations play a role in uncertainty. Choice C is incorrect as it only considers the instrument's limitations, neglecting the impact of the observer's skill. Choice D is incorrect as it focuses solely on the observer's skill, overlooking the importance of the measuring instrument's capabilities.
Which one of the following statements about atomic structure is false?
- A. An atom is mostly empty space.
- B. Almost all of the mass of the atom is concentrated in the nucleus.
- C. The protons and neutrons in the nucleus are very tightly packed.
- D. The number of protons and neutrons is always the same in the neutral atom.
Correct Answer: D
Rationale: The correct answer is D because the statement that the number of protons and neutrons is always the same in a neutral atom is false. In a neutral atom, the number of protons equals the number of electrons, not the number of neutrons. Neutrons are not always equal to the number of protons.
A: An atom is mostly empty space - Correct. This is true because the nucleus is very tiny compared to the overall size of the atom.
B: Almost all of the mass of the atom is concentrated in the nucleus - Correct. This is true because protons and neutrons have much more mass than electrons.
C: The protons and neutrons in the nucleus are very tightly packed - Correct. This is true because protons and neutrons are densely packed within the nucleus.