Convert 2751.4 g to mg.

Correct Answer: C

Rationale: To convert grams to milligrams, you multiply by 1000. So, 2751.4 g * 1000 = 2751.4 mg. Therefore, choice C (275.14 mg) is correct. Choice A is incorrect as it incorrectly moves the decimal point. Choice B is incorrect as it doesn't account for the conversion factor. Choice D is incorrect as it incorrectly uses scientific notation.

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.

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.

Correct Answer: C

Rationale: To find the cost of a gram of gold at $1000 per troy ounce, we divide $1000 by 10 (since 1 troy ounce = 10g). This gives us $100 per gram. Therefore, the correct answer is C: between $10 and $50. Option A is incorrect as it is less than $1, option B is incorrect as it is between $1 and $10, and option D is incorrect as it is between $50 and $100.

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.

Correct Answer: A

Rationale: The correct answer A is determined by knowing that the atomic number of rhenium is 75. Since the element is rhenium-185, the sum of protons and neutrons must equal 185. As the atomic number is 75, the number of protons is 75. Therefore, the number of neutrons is 185 - 75 = 110. Thus, rhenium-185 has 75 protons and 110 neutrons. Choices B, C, and D are incorrect as they do not adhere to the correct number of protons and neutrons in the nucleus of rhenium-185.

Correct Answer: D

Rationale: The correct answer is D: kilometer. A kilometer is a metric unit for length because it is used to measure long distances. In the metric system, length is typically measured in meters, and a kilometer is equal to 1000 meters. This makes it a suitable unit for measuring larger distances efficiently. Explanation for incorrect choices: A: Gram is a unit of mass, not length. B: Milliliter is a unit of volume, not length. C: Yard is a unit of length, but it is not a metric unit. The metric system uses meters and its derivatives for length measurements.

Correct Answer: A

Rationale: The correct answer is A: 2.62 × 10^5. To convert atmospheric pressure from inches of mercury to pascals, we use the conversion factor 1 in. = 2.54 cm and the standard atmospheric pressure at sea level (29.92 in. Hg). First, convert 29.92 in. Hg to cm Hg (29.92 in. × 2.54 cm/in.), then convert cm Hg to Pa (1 atm = 101325 Pa). Follow these steps to get the correct answer. Choice B (1.03 × 10^7) is incorrect as it is too high. Choice C (5.02 × 10^4) is incorrect as it is too low. Choice D (4.30 100) is not a valid numerical expression.

Correct Answer: C

Rationale: To convert grams to milligrams, you multiply by 1000. So, 2751.4 g * 1000 = 2751.4 mg. Therefore, choice C (275.14 mg) is correct. Choice A is incorrect as it incorrectly moves the decimal point. Choice B is incorrect as it doesn't account for the conversion factor. Choice D is incorrect as it incorrectly uses scientific notation.