Nokea
In the reaction 2H2 + O2 → 2H2O, how many moles of oxygen are required to react completely with 4 moles of hydrogen?
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: B
Rationale: The balanced chemical equation indicates that 2 moles of H2 react with 1 mole of O2 to produce 2 moles of H2O. To determine how many moles of O2 are required to react with 4 moles of H2, you can use the mole ratio from the balanced equation: 2 moles of H2 react with 1 mole of O2. Therefore, to react completely with 4 moles of H2, you would need 2 moles of O2 (4 moles H2 · 2 moles H2 per 1 mole O2). Hence, 2 moles of oxygen are required to react completely with 4 moles of hydrogen. Choices A, C, and D are incorrect because they do not reflect the correct stoichiometry as defined by the balanced chemical equation.
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What happens to the potential energy of an object when it is lifted higher above the ground?
- A. Potential energy decreases
- B. Potential energy remains the same
- C. Potential energy increases
- D. Potential energy becomes zero
Correct Answer: C
Rationale: When an object is lifted higher above the ground, its potential energy increases. This is because the higher the object is lifted, the greater its potential energy due to the increased distance from the ground. The formula for gravitational potential energy is PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height above the reference point. Therefore, as the height (h) increases, the potential energy (PE) also increases, making choice C the correct answer. Choices A, B, and D are incorrect because when an object is lifted higher, it gains potential energy rather than losing it, keeping it the same, or becoming zero. Thus, the correct answer is that the potential energy of an object increases when it is lifted higher above the ground.
Which dome-shaped muscular structure separates the chest cavity from the abdominal cavity?
- A. Diaphragm
- B. Sternum
- C. Pericardium
- D. Trachea
Correct Answer: A
Rationale: The diaphragm is the correct answer. It is a dome-shaped muscular structure that separates the chest cavity from the abdominal cavity. The diaphragm plays a crucial role in breathing by contracting and relaxing to change thoracic volume during inhalation and exhalation. The sternum is a flat bone in the center of the chest and is not the structure that separates the chest and abdominal cavities. The pericardium is a membrane that surrounds the heart, not involved in separating cavities. The trachea is the windpipe that connects the larynx to the bronchi and is not the structure that separates the chest and abdominal cavities.
What is the term used to describe the inability of the kidneys to effectively filter waste products from the blood?
- A. Dehydration
- B. Kidney failure
- C. Incontinence
- D. Nephritis
Correct Answer: B
Rationale: Kidney failure is the term used to describe the inability of the kidneys to effectively filter waste products from the blood. Dehydration refers to insufficient fluid intake and not the kidney's filtering function. Incontinence is the loss of bladder control, not related to kidney filtration. Nephritis is the inflammation of the kidneys, not specifically related to the kidneys' inability to filter waste products.
What is the name of the microscopic finger-like projections that increase the surface area for absorption in the small intestine?
- A. Goblet cells
- B. Paneth cells
- C. Villi
- D. Crypts of Lieberk¼hn
Correct Answer: C
Rationale: A) Goblet cells: Goblet cells are specialized cells that secrete mucus to protect the lining of the digestive tract. While important for maintaining the health of the intestines, goblet cells do not increase the surface area for absorption in the small intestine.
B) Paneth cells: Paneth cells are specialized cells found in the small intestine that secrete antimicrobial peptides. They play a role in protecting the intestinal stem cells and maintaining the gut microbiota balance, but they do not increase the surface area for absorption.
C) Villi: Villi are microscopic finger-like projections found in the small intestine that increase the surface area available for absorption of nutrients. Each villus contains blood vessels and lacteals (lymphatic vessels) that help absorb nutrients from digested food.
D) Crypts of Lieberk¼hn: Crypts of Lieberk¼hn are small pits located between the villi
Which muscles play a significant role in the process of forced exhalation by contracting to reduce the thoracic cavity volume?
- A. Diaphragm
- B. External intercostal muscles
- C. Internal intercostal muscles
- D. Abdominal muscles
Correct Answer: D
Rationale: The abdominal muscles play a significant role in forced exhalation by contracting to reduce the thoracic cavity volume. When these muscles contract, the pressure within the thoracic cavity increases, assisting in the expulsion of air from the lungs. This action helps to compress the abdomen and push the diaphragm upwards, further decreasing the volume of the thoracic cavity and aiding in the exhalation process. The diaphragm (Choice A) is mainly involved in inhalation by contracting and moving downward to increase thoracic cavity volume. External intercostal muscles (Choice B) and internal intercostal muscles (Choice C) are primarily involved in the process of inhalation by expanding the thoracic cavity during normal breathing, rather than forced exhalation.