Nokea
The degree of agreement among several measurements of the same quantity is called . It reflects the reproducibility of a given type of measurement.
- A. accuracy
- B. error
- C. precision
- D. significance
Correct Answer: C
Rationale: The correct answer is C: precision. Precision refers to the degree of agreement among repeated measurements of the same quantity. It reflects how close the measurements are to each other, indicating reproducibility. Accuracy (choice A) is about how close a measurement is to the true value, not the agreement among multiple measurements. Error (choice B) is a deviation from the true value and not specifically related to the agreement among measurements. Significance (choice D) is about the importance or relevance of a result, not the consistency of measurements. Therefore, precision is the most appropriate term in this context.
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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.
Manganese makes up 3 10–4 percent by mass of the elements found in a normal healthy body. How many grams of manganese would be found in the body of a person weighing 206 lb? (205 lb = 1 kg)
- A. 0.59 g
- B. 0.12 g
- C. 12 g
- D. 59 g
Correct Answer: A
Rationale: To calculate the grams of manganese in a 206 lb body, first convert pounds to kg (206 lb = 93.44 kg). Then, use the given percentage (3 10–4%) to find the amount of manganese in the body (93.44 kg * 0.0003 = 0.028032 g). Since 205 lb = 1 kg, the correct answer is 0.028032 g or approximately 0.59 g (rounding).
Summary of other choices:
B: Incorrect, this does not consider the correct conversion and percentage calculation.
C: Incorrect, this is a much larger value and does not align with the given percentage.
D: Incorrect, this is also a much larger value and does not align with the given percentage.
All of the following are true except:
- A. Ions are formed by adding electrons to a neutral atom.
- B. Ions are formed by changing the number of protons in an atom's nucleus.
- C. Ions are formed by removing electrons from a neutral atom.
- D. An ion has a positive or negative charge.
Correct Answer: B
Rationale: The correct answer is B because changing the number of protons in an atom's nucleus would result in a different element, not an ion.
A: True - adding or removing electrons forms ions.
C: True - removing electrons forms positively charged ions.
D: True - ions have a charge due to the imbalance of protons and electrons.
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.
If the Thomson model of the atom had been correct, Rutherford would have observed:
- A. Alpha particles going through the foil with little or no deflection.
- B. Alpha particles greatly deflected by the metal foil.
- C. Alpha particles bouncing off the foil.
- D. Positive particles formed in the foil.
Correct Answer: B
Rationale: The correct answer is B: Alpha particles greatly deflected by the metal foil. In the Thomson model, the atom was thought to be a uniform, positively charged sphere. If this model had been correct, alpha particles would have passed through the foil with little or no deflection. However, Rutherford observed significant deflections, indicating a concentrated positive charge at the center (nucleus). This aligns with the concept of the Rutherford model of the atom. Choices A, C, and D are incorrect because they do not correspond to the experimental observations made by Rutherford.