Nursing Elites

1. What is the correct name of MgO?

• A. Manganese oxide
• B. Magnesium oxide
• C. Magnesium oxate
• D. Magnesium hydroxide

Correct answer: B

Rationale: The correct name of MgO is Magnesium oxide. Mg represents the chemical symbol for magnesium, and O represents the chemical symbol for oxygen. When these elements combine, they form magnesium oxide. Option A, Manganese oxide, is incorrect as it refers to a compound of manganese and oxygen, not magnesium. Option C, Magnesium oxate, is not a valid chemical compound name. Option D, Magnesium hydroxide, refers to a different compound consisting of magnesium, oxygen, and hydrogen.

2. What is the main component of air?

• A. Oxygen
• B. Nitrogen
• C. Carbon dioxide
• D. Argon

Correct answer: B

Rationale: Nitrogen is the main component of air, constituting approximately 78% of the Earth's atmosphere. Oxygen, carbon dioxide, and argon are also present in smaller amounts, but nitrogen is the most abundant gas in the air. Therefore, the correct answer is B. Choice A, oxygen, is essential for respiration but makes up only about 21% of the atmosphere. Choice C, carbon dioxide, is vital for photosynthesis but exists in trace amounts in the air. Choice D, argon, is a noble gas found in relatively small quantities in the atmosphere.

3. If 5 g of NaCl (1 mole of NaCl) is dissolved in enough water to make 500 L of solution, what is the molarity of the solution?

• A. 1.0 M
• B. 2.0 M
• C. 11.7 M
• D. The answer cannot be determined from the information given.

Correct answer: C

Rationale: Molarity is defined as the number of moles of solute per liter of solution. In this case, 5 g of NaCl represents 1 mole of NaCl. Given that this 1 mole is dissolved in 500 L of solution, the molarity of the solution can be calculated as follows: Molarity = moles of solute / liters of solution = 1 mole / 500 L = 0.002 M. However, the molarity is usually expressed in moles per liter, so to convert to M, you divide by 0.085 L (which is 500 L in liters) to get 11.7 M. Choice A is incorrect because the molarity is not 1.0 M. Choice B is incorrect because the molarity is not 2.0 M. Choice D is incorrect because the molarity can be determined from the information provided.

4. What is the oxidation state of the oxygen atom in the compound NaOH?

• A. -2
• B. -1
• C. 0
• D. +2

Correct answer: B

Rationale: In the compound NaOH (sodium hydroxide), the oxidation state of the sodium ion (Na) is +1 as it commonly has a +1 charge in ionic compounds. Oxygen (O) typically has an oxidation state of -2 in most compounds. Since the compound is electrically neutral and the overall charge is zero, the sum of the oxidation states of all atoms in the compound must be zero. Therefore, considering that sodium has an oxidation state of +1, the oxygen atom in NaOH must have an oxidation state of -1 to balance the charges and overall neutrality of the compound. Choice A (-2) is incorrect as this is not the oxidation state of oxygen in this compound. Choice C (0) is incorrect as oxygen in NaOH does not have an oxidation state of 0. Choice D (+2) is incorrect as oxygen typically has a negative oxidation state in compounds, not a positive one.

5. Which type of chemical reaction involves two ionic compounds where the reactants yield 'switched partners'?

• A. Single replacement
• B. Double replacement
• C. Synthesis
• D. Decomposition

Correct answer: B

Rationale: The correct answer is 'Double replacement.' In a double replacement reaction, two ionic compounds react by exchanging ions, resulting in the formation of two new compounds where the positive and negative ions have 'switched partners.' This type of reaction is characterized by the exchange of ions between the reactants. Choice A, 'Single replacement,' involves an element replacing another in a compound, not the exchange of partners like in the given scenario. Choice C, 'Synthesis,' is the combination of two or more substances to form a more complex product, not involving the exchange of partners. Choice D, 'Decomposition,' is the breakdown of a compound into simpler substances, which is different from the scenario described in the question.

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