Nokea
A species with 12 protons and 10 electrons is
- A. Ne2+
- B. Ti2+
- C. Mg2+
- D. Ne2–
Correct Answer: C
Rationale: The correct answer is C: Mg2+. A species with 12 protons must have an atomic number of 12, which corresponds to magnesium (Mg). The 10 electrons indicate that it has a 2+ charge, making it Mg2+. Choice A (Ne2+) is incorrect because neon (Ne) has an atomic number of 10, not 12. Choice B (Ti2+) is incorrect because titanium (Ti) has an atomic number of 22, not 12. Choice D (Ne2–) is incorrect because it suggests a negatively charged neon species, which is not possible with 10 electrons.
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The melting point of picolinic acid is 5°C. What is the melting point of picolinic acid on the Fahrenheit scale?
- A. 107.8°F
- B. 245.7°F
- C. 168.5°F
- D. 409.5°F
Correct Answer: A
Rationale: The correct answer is A: 107.8°F. To convert Celsius to Fahrenheit, you use the formula °F = (°C x 9/5) + 32. Substituting 5°C into the formula gives (5 x 9/5) + 32 = 41 + 32 = 73°F. Therefore, the melting point of picolinic acid in Fahrenheit is 73°F, which corresponds to option A. Option B, C, and D are incorrect because they do not match the calculated Fahrenheit temperature.
Which of the following metric relationships is incorrect?
- A. 1 microliter = 10–6 liters
- B. 1 gram = 103 kilograms
- C. 103 milliliters = 1 liter
- D. 1 gram = 102 centigrams
Correct Answer: B
Rationale: The correct answer is B: 1 gram = 10^3 kilograms. This is incorrect because 1 kilogram is equal to 1000 grams, not 100 grams. A is correct as 1 microliter is indeed 10^-6 liters. C is correct as 10^3 milliliters equals 1 liter. D is correct as 1 gram is equal to 10^2 centigrams. The incorrect relationship in choice B violates the metric system conversion factor of 1 kilogram being equal to 1000 grams.
A scientist obtains the number 0.045006700 on a calculator. If this number
actually has four significant figures, how should it be written?
- A. 0.4567
- B. 0.4501
- C. 0.045
- D. 0.045
Correct Answer: C
Rationale: The correct answer is C: 0.045. When dealing with significant figures, trailing zeros after the decimal point are considered significant. In this case, the number 0.045006700 should be rounded to 0.045 since it has four significant figures. Choice A has too many significant figures, B rounds incorrectly, and D removes significant figures after the decimal point. Thus, C is the correct choice.
Express the volume 781.2CM3 in liters.
- A. 781.2 L
- B. 78.12 L
- C. 7.812 L
- D. 0.7812 L
Correct Answer: D
Rationale: To convert cm3 to liters, divide by 1000 as 1 liter = 1000 cm3.
Therefore, 781.2 cm3 ÷ 1000 = 0.7812 L.
Correct answer is D: 0.7812 L.
Other choices are incorrect as they do not reflect the correct conversion from cm3 to liters.
You are asked to determine the perimeter of the cover of your textbook. You measure the length as 36 cm and the width as 83 cm. How many significant figures should you report for the perimeter?
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: C
Rationale: The correct answer is C (3 significant figures). When calculating the perimeter of a rectangle, you add all the sides together. In this case, the perimeter would be 2(36 cm + 83 cm) = 238 cm. The least precise measurement given (83 cm) has 2 significant figures. Therefore, the final answer should be reported with the same number of significant figures as the least precise measurement, which is 3.
Summary:
A: 1 significant figure is too few.
B: 2 significant figures are based on the least precise measurement.
D: 4 significant figures are too many as it should match the least precise measurement.