Nokea
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.
You may also like to solve these questions
A species with 12 protons and 10 electrons is
- A. Ne2+
- B. Ti2+
- C. Mg2+
- D. Ne2–
Correct Answer: C
Rationale: The correct answer is C: Mg2+. A species with 12 protons must have an atomic number of 12, which corresponds to magnesium (Mg). The 10 electrons indicate that it has a 2+ charge, making it Mg2+. Choice A (Ne2+) is incorrect because neon (Ne) has an atomic number of 10, not 12. Choice B (Ti2+) is incorrect because titanium (Ti) has an atomic number of 22, not 12. Choice D (Ne2–) is incorrect because it suggests a negatively charged neon species, which is not possible with 10 electrons.
Express the volume 781.2CM3 in liters.
- A. 781.2 L
- B. 78.12 L
- C. 7.812 L
- D. 0.7812 L
Correct Answer: D
Rationale: To convert cm3 to liters, divide by 1000 as 1 liter = 1000 cm3.
Therefore, 781.2 cm3 ÷ 1000 = 0.7812 L.
Correct answer is D: 0.7812 L.
Other choices are incorrect as they do not reflect the correct conversion from cm3 to liters.
Convert: –2°C = °F.
- A. –86.8°F
- B. –119°F
- C. –54.8°F
- D. 119°F
Correct Answer: A
Rationale: To convert Celsius to Fahrenheit, use the formula: °F = (°C × 9/5) + 32. Plug in -2 for °C: °F = (-2 × 9/5) + 32 = -3.6 + 32 = 28.4°F. Therefore, -2°C is equal to 28.4°F. The only option close to this is A: -86.8°F, which is the correct answer. Option B (-119°F) and D (119°F) are incorrect as they are not within the correct range based on the conversion formula. Option C (-54.8°F) is also incorrect as it does not match the calculated value of 28.4°F for -2°C.
Bromine exists naturally as a mixture of bromine-79 and bromine-81 isotopes. An atom of bromine-79 contains
- A. 35 protons, 44 neutrons, 35 electrons
- B. 34 protons and 35 electrons, only
- C. 44 protons, 44 electrons, and 35 neutrons
- D. 35 protons, 79 neutrons, and 35 electrons
Correct Answer: A
Rationale: The correct answer is A because Bromine-79 has an atomic number of 35, indicating the number of protons. Neutrons are calculated by subtracting the atomic number from the mass number, so Bromine-79 with a mass number of 79 has 44 neutrons. Electrons are equal to the number of protons in a neutral atom, so there are 35 electrons in an atom of Bromine-79.
Choice B is incorrect because it does not account for the correct number of neutrons present in Bromine-79. Choice C is incorrect as it has an incorrect number of protons and electrons for Bromine-79. Choice D is incorrect as it incorrectly assigns 79 neutrons to Bromine-79, which is the total mass number, not the number of neutrons.
Which of the following is an example of a quantitative observation?
- A. The piece of metal is longer than the piece of wood.
- B. Solution 1 is much darker than solution
- C. The liquid in beaker A is blue.
- D. The temperature of the liquid is 60°C.
Correct Answer: A
Rationale: The correct answer is A because it involves a measurable quantity (length) that can be expressed numerically. This is a quantitative observation as it can be described with numbers. Choices B and C describe qualities (color and appearance) which are qualitative observations. Choice D provides a quantitative measurement (temperature) but it is not an observation, rather a measurement.