Nokea
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.
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In March 2008, gold reached a milestone value of $1000 per troy ounce. At that price, what was the cost of a gram of gold? (1 troy ounce = 10 g)
- A. less than $1
- B. between $1 and $10
- C. between $10 and $50
- D. between $50 and $100
Correct Answer: C
Rationale: To find the cost of a gram of gold at $1000 per troy ounce, we divide $1000 by 10 (since 1 troy ounce = 10g). This gives us $100 per gram. Therefore, the correct answer is C: between $10 and $50. Option A is incorrect as it is less than $1, option B is incorrect as it is between $1 and $10, and option D is incorrect as it is between $50 and $100.
The density of liquid mercury is 6 g/mL. What is its density in units of ? (54 cm = 1 in., 205 lb = 1 kg)
- A. 1.57 10 2
- B. 4.91 10 1
- C. 1.01 10 1
- D. 7.62 10 2
Correct Answer: C
Rationale: To find the density of liquid mercury in units of g/cm³, we need to convert the density from g/mL to g/cm³. The conversion factor is 1 mL = 1 cm³. Given the density of mercury as 6 g/mL, it is equivalent to 6 g/cm³. Therefore, the correct answer is 1.01 x 10¹ g/cm³ (choice C).
Choice A: 1.57 x 10² is too large for the density of liquid mercury.
Choice B: 4.91 x 10¹ is incorrect as it does not match the calculated density.
Choice D: 7.62 x 10² is significantly higher than the actual density of liquid mercury.
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.
A 0 mL sample of glycerol has a mass of 2 grams. What is the mass of a 57-mL sample of glycerol?
- A. 8.8 g
- B. 45 g
- C. 2.9 104 g
- D. 72 g
Correct Answer: B
Rationale: To find the mass of a 57-mL sample of glycerol, we use the given mass-to-volume ratio. Since 0 mL has a mass of 2 grams, the mass-to-volume ratio is 2g/0mL = 2g/mL. Therefore, for a 57-mL sample, we multiply 2g/mL by 57 mL to get 114 grams, which corresponds to answer choice B.
Choice A (8.8 g) is incorrect because it does not align with the calculated mass of 114 g for a 57-mL sample. Choices C (2.9 104 g) and D (72 g) are also incorrect as they are not consistent with the mass-to-volume ratio of 2g/mL provided in the question.
The formula of water, H O, suggests:
- A. There is twice as much mass of hydrogen as oxygen in each molecule.
- B. There are two hydrogen atoms and one oxygen atom per water molecule.
- C. There is twice as much mass of oxygen as hydrogen in each molecule.
- D. There are two oxygen atoms and one hydrogen atom per water molecule.
Correct Answer: B
Rationale: The formula for water is H₂O, indicating there are two hydrogen atoms and one oxygen atom per molecule. This is because the subscript 2 in H₂ represents two hydrogen atoms, and O represents one oxygen atom. Therefore, choice B is correct. Choices A, C, and D are incorrect because they do not accurately represent the composition of water molecules. Choice A suggests twice as much mass of hydrogen than oxygen, which is not true. Choice C suggests twice as much mass of oxygen than hydrogen, which is also incorrect. Choice D implies there are two oxygen atoms in a water molecule, which is inaccurate.