Nursing Elites

1. Nuclear fusion powers the sun and other stars. What is the main obstacle to achieving controlled nuclear fusion on Earth for energy production?

• A. Lack of suitable materials to handle high temperatures and pressures.
• B. Limited availability of fusion fuels like deuterium and tritium.
• C. Difficulty in containing the plasma where fusion occurs.
• D. All of the above

Correct answer: D

Rationale: The main obstacle to achieving controlled nuclear fusion on Earth for energy production involves a combination of factors. A) Lack of suitable materials to handle high temperatures and pressures is a significant challenge due to the extreme conditions required for fusion reactions. B) Limited availability of fusion fuels like deuterium and tritium can pose a constraint on the scalability and sustainability of fusion energy. C) Difficulty in containing the plasma where fusion occurs is another critical issue as plasma instabilities and heat losses can hinder the efficiency of fusion reactions. Therefore, all of the options (A, B, and C) contribute to the challenges in achieving controlled nuclear fusion for energy production on Earth.

2. When two objects with different masses collide, what happens to their momentum after the collision?

• A. Increases for both objects
• B. Decreases for both objects
• C. Remains the same for both objects
• D. Can increase for one and decrease for the other

Correct answer: C

Rationale: When two objects with different masses collide, their total momentum remains the same after the collision according to the law of conservation of momentum if no external forces are acting on them. This means that the momentum of each individual object may change, but the sum of their momenta will remain constant. Choice A is incorrect because the total momentum of the system is conserved. Choice B is incorrect because momentum is conserved in an isolated system. Choice D is incorrect as it implies a violation of the law of conservation of momentum, which states that the total momentum of an isolated system remains constant.

3. How many moles of water are produced when 0.5 moles of methane (CH4) react with excess oxygen?

• A. 0.5 moles
• B. 1 mole
• C. 2 moles
• D. 3 moles

Correct answer: B

Rationale: The balanced chemical equation for the combustion of methane is: CH4 + 2O2 -> CO2 + 2H2O. This equation shows that 1 mole of methane produces 2 moles of water. Therefore, when 0.5 moles of methane react, they will produce 1 mole of water. The ratio of water to methane is 2:1, meaning that for every mole of methane that reacts, it produces 2 moles of water. Since only 0.5 moles of methane are reacting, the amount of water produced will be half of what would be produced if 1 mole of methane reacted, resulting in 1 mole of water being produced. Choice A is incorrect because it does not consider the stoichiometry of the reaction. Choices C and D are incorrect as they do not align with the balanced chemical equation and the stoichiometric ratios involved in the reaction.

4. Deuterium, a stable isotope of hydrogen, has a nucleus containing:

• A. A single proton
• B. A proton and a neutron
• C. Two protons and an electron
• D. Two neutrons

Correct answer: B

Rationale: Deuterium, as an isotope of hydrogen, has an atomic number of 1 and a mass number of 2. The nucleus of deuterium contains one proton (as in all hydrogen atoms) and one neutron, totaling 2 nucleons in the nucleus. Therefore, the correct answer is that deuterium's nucleus contains a proton and a neutron. Choices A, C, and D are incorrect. Deuterium is not just a single proton (A), doesn't have two protons and an electron (C), and doesn't contain two neutrons (D). The correct composition of deuterium's nucleus is one proton and one neutron.

5. What is the periodic table?

• A. A table of elements that are arranged in order of increasing atomic number.
• B. A table of elements that are arranged in order of increasing atomic mass.
• C. A table of elements that are arranged in order of their reactivity.
• D. A table of elements that are arranged in order of their color.

Correct answer: A

Rationale: The periodic table is a tabular arrangement of the chemical elements, organized based on their atomic number, electron configurations, and recurring chemical properties. Elements are placed in rows (periods) and columns (groups) with similar properties. The elements are listed in order of increasing atomic number, which is the number of protons in the nucleus of an atom. This arrangement reveals a periodic repetition of chemical properties, forming the basis of the periodic law. Choice B, which suggests arranging elements based on increasing atomic mass, is incorrect because the periodic table is primarily organized by atomic number, not atomic mass. Choices C and D are also incorrect as the periodic table is not based on reactivity or color of elements, but rather on atomic number and properties.

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