Nokea
In 1984, some drums of uranium hexafluoride were lost in the English Channel, which is known for its cold water (about 17°C). The melting point of uranium hexafluoride is 148°F. In what physical state is the uranium hexafluoride in these drums?
- A. solid
- B. liquid
- C. gas
- D. a mixture of solid and liquid
Correct Answer: A
Rationale: The correct answer is A: solid. Uranium hexafluoride has a melting point of 148°F, which is equivalent to approximately 64.4°C. Since the water temperature in the English Channel is only about 17°C, the uranium hexafluoride would be below its melting point and thus in a solid state. The other choices are incorrect because the temperature is not high enough for it to be in a liquid or gaseous state, and there is no indication of it being a mixture of solid and liquid based on the given information.
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The numbers of protons, neutrons, and electrons in K+ are: A) 20 p, 19 n, 19 e
- A. 20 p, 19 n, 20 e
- B. 19 p, 20 n, 20 e
- C. 19 p, 20 n, 19 e
- D. 19 p, 20 n, 18 e
Correct Answer: C
Rationale: The correct answer is C: 19 p, 20 n, 19 e. K+ has an atomic number of 19, indicating 19 protons. Since it is a potassium ion with a +1 charge, it lost one electron, giving it 19 electrons instead of the usual 20. The number of neutrons is found by subtracting the atomic number from the mass number (39 for potassium) to get 20 neutrons. Option A is incorrect due to the incorrect number of electrons. Option B has the incorrect number of protons. Option D has the incorrect number of electrons.
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
As warm water sits in a cool room, you measure the temperature change ( T = T – final T ). Which of the following is true? initial
- A. The temperature change ( T) is bigger if you are measuring in °F.
- B. The temperature change ( T) is bigger if you are measuring in °C.
- C. The temperature change ( T) will be the same regardless of the scale you use.
- D. Answer A or B is correct, depending on the difference in temperature between the water and the room.
Correct Answer: A
Rationale: The correct answer is A. When measuring temperature change, the size of the change will depend on the scale used. In Fahrenheit (°F), the scale has larger degrees compared to Celsius (°C). Therefore, the temperature change will appear bigger when measured in Fahrenheit. This is because each degree Fahrenheit is smaller in magnitude compared to each degree Celsius.
Choices B and C are incorrect. In choice B, the temperature change will not be bigger if measured in °C because each degree Celsius is larger in magnitude compared to each degree Fahrenheit. Choice C is incorrect because the temperature change does depend on the scale used.
Choice D is incorrect because the difference in temperature between the water and the room does not affect the scale used for measurement. The scale itself determines the magnitude of the temperature change.
Convert 9 kg to lb. (1 kg = 205 lb)
- A. 17 lbs
- B. 1.7 lbs
- C. 3.6 lbs
- D. 0.017 lbs
Correct Answer: A
Rationale: To convert 9 kg to lb, we multiply 9 kg by the conversion factor of 2.205 lb/kg.
9 kg * 2.205 lb/kg = 19.845 lb, which is approximately 20 lb.
Among the choices, 17 lbs (option A) is the closest to 20 lb, making it the correct answer.
Option B (1.7 lbs), C (3.6 lbs), and D (0.017 lbs) are all significantly lower and do not match the conversion calculation.
The density of gasoline is 7025 g/mL at 20°C. When gasoline is added to water:
- A. It will float on top.
- B. It will sink to the bottom.
- C. It will mix so, you can't see it.
- D. The mixture will improve the running of the motor.
Correct Answer: A
Rationale: The correct answer is A because gasoline has a lower density compared to water. Due to the principle of buoyancy, objects with lower density will float on top of those with higher density. Gasoline will float on top of water because it is less dense. Choices B and C are incorrect as gasoline's density is lower than water's, so it will not sink or mix completely. Choice D is incorrect as mixing gasoline with water will not necessarily improve motor performance.