Nokea
In the reaction 2Na + 2H2O → 2NaOH + H2, what is the limiting reactant when 3 moles of sodium react with 2 moles of water?
- A. Na
- B. H2O
- C. NaOH
- D. H2
Correct Answer: A
Rationale: The balanced chemical equation indicates that 2 moles of sodium react with 2 moles of water to yield 2 moles of sodium hydroxide and 1 mole of hydrogen gas. When 3 moles of sodium react with only 2 moles of water, sodium becomes the limiting reactant as it is present in excess compared to the available water molecules. This situation arises because not all sodium atoms can fully react with the limited amount of water, resulting in sodium being the limiting reactant in this specific case. Choice B (H2O), choice C (NaOH), and choice D (H2) are incorrect as they are not the limiting reactant in the given reaction scenario.
You may also like to solve these questions
The innate immune system provides a non-specific first line of defense. What are some physical barriers that contribute to the innate immune system?
- A. Antibodies
- B. Phagocytes
- C. Skin and mucous membranes
- D. Memory B cells
Correct Answer: C
Rationale: Physical barriers such as the skin and mucous membranes are crucial components of the innate immune system's first line of defense. These barriers act as physical obstacles that prevent pathogens from entering the body. Antibodies (option A) are produced by the adaptive immune system in response to specific pathogens and do not serve as physical barriers. Phagocytes (option B) are cells that engulf and digest pathogens, playing a role in the innate immune response but not as physical barriers. Memory B cells (option D) are part of the adaptive immune system and aid in mounting a faster and more effective immune response upon subsequent exposure to a specific pathogen, but they are not physical barriers against initial pathogen entry.
Chyle, a milky white fluid, is transported by lymphatic vessels from the:
- A. Lungs
- B. Intestines
- C. Kidneys
- D. Skin
Correct Answer: B
Rationale: Chyle, a milky white fluid, is formed in the small intestine during digestion. It is composed of lymph and emulsified fats. Lymphatic vessels in the intestines, specifically lacteals, transport chyle from the intestines to the bloodstream for the distribution of nutrients throughout the body. The transport of chyle from the lungs, kidneys, or skin is not correct as these organs are not primarily involved in the production or transportation of chyle.
What is the term for a group of organisms that can interbreed and produce fertile offspring?
- A. Genus
- B. Phylum
- C. Kingdom
- D. Species
Correct Answer: D
Rationale: A species is defined as a group of organisms that can interbreed and produce fertile offspring, which is a fundamental concept in biology. This ability to interbreed and produce fertile offspring is a key characteristic that distinguishes one species from another. Genus (option A) refers to a taxonomic rank that includes one or more closely related species, not the ability to interbreed. Phylum (option B) and kingdom (option C) are higher taxonomic ranks that encompass a broader range of organisms, not specifically defined by interbreeding and fertile offspring production. Therefore, the correct answer is 'Species.'
What is the difference between a real image and a virtual image formed by a lens?
- A. Real images can be projected onto a screen, while virtual images cannot.
- B. Real images are always upright, while virtual images can be inverted.
- C. Real images are formed by converging lenses, while virtual images are formed by diverging lenses.
- D. All of the above are true.
Correct Answer: A
Rationale: The correct answer is A. Real images can be projected onto a screen because they are formed by the actual convergence of light rays, while virtual images cannot be projected onto a screen as they appear to diverge from a point behind the lens. Real and virtual images do not have a consistent orientation (upright or inverted), so option B is incorrect. Real images are formed by both converging and diverging lenses depending on the specific scenario, so option C is not a definitive distinction. Option D is incorrect as not all the statements are true. Therefore, the only accurate general distinction between real and virtual images is that real images can be projected onto a screen, while virtual images cannot.
What does the T wave on an ECG correspond to?
- A. Atrial depolarization
- B. Ventricular depolarization
- C. Atrial repolarization
- D. Ventricular repolarization
Correct Answer: D
Rationale: The T wave on an ECG corresponds to ventricular repolarization. Following ventricular depolarization, which is represented by the QRS complex, the ventricles undergo repolarization during the T wave. This phase signifies the recovery of ventricular muscle cells as they prepare for the subsequent depolarization cycle. Choices A, B, and C are incorrect because the T wave specifically reflects the repolarization of the ventricles, not the atria or their respective depolarization or repolarization phases.