Nokea
The pressure of the earth's atmosphere at sea level is . What is the pressure when expressed in ? (54 cm = 1 in., 205 lb = 1 kg)
- A. 2.62 105
- B. 1.03 107
- C. 5.02 104
- D. 4.30 100
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.
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Avogadro's hypothesis states that:
- A. Each atom of oxygen is 16 times more massive than an atom of hydrogen.
- B. A given compound always contains exactly the same proportion of elements by mass.
- C. When two elements form a series of compounds, the ratios of masses that combine with 1 gram of the first element can always be reduced to small whole numbers.
- D. At the same temperature and pressure, equal volumes of different gases contain an equal number of particles.
Correct Answer: D
Rationale: Rationale for correct answer D: Avogadro's hypothesis states that equal volumes of different gases at the same temperature and pressure contain an equal number of particles. This is because gases behave similarly under these conditions due to the ideal gas law. Avogadro's hypothesis is crucial in understanding the behavior of gases and is fundamental in the study of chemistry.
Summary of incorrect choices:
A: This statement is about the relative mass of atoms of different elements, not Avogadro's hypothesis.
B: This statement relates to the law of definite proportions, not Avogadro's hypothesis.
C: This statement refers to the law of multiple proportions, not Avogadro's hypothesis.
The numbers of protons, neutrons, and electrons in K+ are: A) 20 p, 19 n, 19 e
- A. 20 p, 19 n, 20 e
- B. 19 p, 20 n, 20 e
- C. 19 p, 20 n, 19 e
- D. 19 p, 20 n, 18 e
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.
Convert 4 lb to g. (1 lb = 6 g)
- A. 7.58 10 2 g
- B. 1.56 103 g
- C. 7.58 104 g
- D. 1.56 102 g
Correct Answer: C
Rationale: To convert 4 lb to g, we use the conversion factor provided: 1 lb = 6 g.
1. Multiply 4 lb by 6 g/lb: 4 lb * 6 g/lb = 24 g.
2. Since the question asks for the answer in grams, the correct conversion is 24 g.
Therefore, the correct answer is C (7.58 x 10^4 g).
Other choices are incorrect because they do not correctly apply the conversion factor or provide the accurate conversion from pounds to grams.
Consider the numbers 23.68 and 4.12. The sum of these numbers has
significant figures, and the product of these numbers has _
significant figures.
- A. 3, 3
- B. 4, 4
- C. 3, 4
- D. 4, 3
Correct Answer: D
Rationale: To determine the significant figures in the sum of 23.68 and 4.12, we add the numbers which results in 27.8. The sum has 3 significant figures because the least precise number has 2 decimal places.
To find the significant figures in the product, we multiply the numbers which equals 97.4096. The product has 4 significant figures since the number with the fewest significant figures has 2 before the decimal point and 4 after.
Therefore, the correct answer is D (4 significant figures in the product and 3 in the sum).
20 protons
- A. 22 protons
- B. 20 protons
- C. 18 electrons
- D. 22
Correct Answer: A
Rationale: The correct answer is A. Since the question states that there are 20 protons, option A with 22 protons is incorrect. Option B with 20 protons matches the given information, making it the correct answer. Option C with 18 electrons is unrelated to the given information about protons. Option D with just the number 22 is irrelevant and does not provide any information about protons.