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.
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The density of oleic acid is 895 g / mL. What is the thickness of the monolayer (the length of an oleic acid molecule)?
- A. cm
- B. cm
- C. cm
- D. cm
Correct Answer: B
Rationale: The correct answer is B. To calculate the thickness of the monolayer, we need to use the formula thickness = density / (Avogadro's number * molecular weight). Given the density of oleic acid (895 g/mL), we can substitute this value along with the molecular weight of oleic acid into the formula. By dividing the density by the product of Avogadro's number and the molecular weight, we obtain the thickness in cm. The other choices are incorrect because they do not consider the given density and relevant constants in the calculation. Choice A, C, and D do not follow the correct formula for determining the thickness of the monolayer.
The agreement of a particular value with the true value is called
- A. accuracy
- B. error
- C. precision
- D. significance
Correct Answer: A
Rationale: The correct answer is A: accuracy. Accuracy refers to how close a measured value is to the true value. It indicates the absence of systematic errors. Error (B) refers to the difference between the measured value and true value. Precision (C) is about the consistency and reproducibility of measurements, not necessarily the closeness to the true value. Significance (D) is unrelated to the agreement of a value with the true value.
The melting point of indium is 2°C. At 323°F, what is the physical state of indium?
- A. Solid.
- B. Liquid.
- C. Gas.
- D. Not enough information.
Correct Answer: B
Rationale: To determine the physical state of indium at 323°F, we convert the temperature to Celsius (323°F = 161.7°C). Since the melting point of indium is 2°C, which is lower than 161.7°C, indium would be in a liquid state at 323°F. The correct choice is B: Liquid.
A: Solid - Incorrect because indium is in a liquid state at 323°F.
C: Gas - Incorrect, as indium would be in a liquid state at 323°F.
D: Not enough information - Incorrect since the temperature provided allows us to determine the physical state of indium.
How many significant figures should be reported for the difference between 6172 mL and 57 mL?
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: B
Rationale: To determine the significant figures in the difference between 6172 mL and 57 mL, subtract the numbers: 6172 mL - 57 mL = 6115 mL. The answer should have the same number of decimal places as the number with the fewest decimal places in the subtraction, which is 57 mL. Hence, the correct answer is 2 significant figures. Choice A is incorrect because it is too low as it does not account for the 1 in the tens place of 57 mL. Choice C is incorrect as it is too high because the answer does not have that many significant figures. Choice D is incorrect as it also overestimates the number of significant figures in the difference.
The first scientist to show that atoms emit any negative particles was
- A. J. J. Thomson
- B. Lord Kelvin
- C. Ernest Rutherford
- D. William Thomson
Correct Answer: A
Rationale: Step-by-step rationale:
1. J.J. Thomson discovered the electron in 1897 through his cathode ray experiment.
2. Electrons are negatively charged particles emitted by atoms.
3. This groundbreaking discovery proved atoms emit negative particles.
4. Therefore, J.J. Thomson is the correct answer.
Summary:
- Lord Kelvin focused on thermodynamics, not subatomic particles.
- Ernest Rutherford discovered the nucleus, not electrons.
- William Thomson, also known as Lord Kelvin, did not directly contribute to the discovery of negative particles emitted by atoms.