Nokea
The chemist credited for inventing a set of symbols for writing elements and a system for writing the formulas of compounds (and for discovering selenium, silicon, and thorium) is
- A. Boyle
- B. Lavoisier
- C. Priestly
- D. Berzelius
Correct Answer: D
Rationale: The correct answer is D: Berzelius. Berzelius is credited with inventing symbols for elements and a system for writing compound formulas. He also discovered selenium, silicon, and thorium. Berzelius made significant contributions to the field of chemistry.
A: Boyle is known for Boyle's Law related to gases, not for inventing chemical symbols or discovering elements.
B: Lavoisier is known as the father of modern chemistry but did not invent chemical symbols or discover these elements.
C: Priestly is known for discovering oxygen, but not for the specific contributions mentioned in the question.
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Alpha particles beamed at thin metal foil may
- A. pass directly through without changing direction
- B. be slightly diverted by attraction to electrons
- C. be reflected by direct contact with nuclei
- D. A and C
Correct Answer: D
Rationale: The correct answer is D because when alpha particles are beamed at a thin metal foil, some pass directly through due to their small size and high energy (option A), while others are reflected by direct contact with nuclei in the metal foil (option C). This is based on the Rutherford scattering experiment which showed that alpha particles can be deflected by the positive nuclei in the metal foil. Option B is incorrect as alpha particles are not diverted by attraction to electrons in the foil. Option D combines the correct explanations for the behavior of alpha particles when beamed at thin metal foil.
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.
Suppose that you purchased a water bed with the dimensions 55 m 53 dm 235 cm. What mass of water does this bed contain?
- A. 1.52 103 g
- B. 1.52 104 g
- C. 1.52 105 g
- D. 1.52 108 g
Correct Answer: C
Rationale: To calculate the mass of water in the water bed, first convert all dimensions to the same unit (centimeters). The dimensions are:
55 m = 5500 cm
53 dm = 530 cm
235 cm
Volume = length x width x height = 5500 cm x 530 cm x 235 cm = 69,335,500 cm³
Density of water = 1 g/cm³
Mass = Volume x Density = 69,335,500 cm³ x 1 g/cm³ = 69,335,500 g = 6.93 x 10^7 g
Therefore, the correct answer is C: 1.52 x 10^5 g. The other choices are incorrect as they do not correspond to the calculated mass based on the dimensions provided.
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.