Nokea
Which of the following units is used to express concentration as a mass of solute per unit volume of solution?
- A. Molality (m)
- B. Molarity (M)
- C. Weight percent (%)
- D. Parts per million (ppm)
Correct Answer: A
Rationale: Molality (m) is the unit used to express concentration as a mass of solute per unit volume of solution. It is calculated by dividing the mass of solute in grams by the mass of the solvent in kilograms. Molality is preferred over molarity when there are large temperature variations as it is temperature-independent, making it a more accurate measure of concentration. Molarity (B) is the unit used to express concentration as moles of solute per liter of solution, weight percent (C) is the mass of solute per 100 parts of the total mass of the solution, and parts per million (D) is used to express very small concentrations where 1 ppm is equivalent to 1 mg of solute per liter of solution.
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What is the product of the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH)?
- A. NaCl + H2O
- B. NaOH + HCl
- C. Na2Cl + H2O
- D. NaClO3 + H2
Correct Answer: A
Rationale: When hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), it forms sodium chloride (NaCl) and water (H2O) according to the following chemical equation: HCl + NaOH -> NaCl + H2O. Therefore, the correct answer is NaCl + H2O (Choice A). This reaction is a classic acid-base neutralization reaction where the acid (HCl) reacts with the base (NaOH) to form a salt (NaCl) and water (H2O). Choice B (NaOH + HCl) is incorrect because the order of the reactants matters in a chemical reaction, and in this case, HCl is the acid reacting with NaOH. Choices C (Na2Cl + H2O) and D (NaClO3 + H2) are incorrect because they do not represent the products of the reaction between HCl and NaOH as per the balanced chemical equation.
According to Newton's third law of motion, for every action, there is an equal and opposite _________.
- A. Reaction
- B. Force
- C. Acceleration
- D. Momentum
Correct Answer: A
Rationale: Newton's third law of motion states that for every action, there is an equal and opposite reaction. This law emphasizes that forces always exist in pairs. When one object exerts a force on a second object (action), the second object exerts an equal force in the opposite direction back on the first object (reaction). This principle is crucial in understanding the interactions between objects and the resulting motion observed in the physical world. Choices B, C, and D are incorrect because while force is involved, the specific concept highlighted by Newton's third law is the equal and opposite reaction. Acceleration and momentum are also related to motion but are not directly tied to Newton's third law of motion, which focuses on the equality and oppositeness of forces in interactions.
Myelin sheath is a fatty substance that insulates and protects the long extensions of some nerve cells. It is produced by:
- A. Schwann cells
- B. Astrocytes
- C. Neurons
- D. Oligodendrocytes
Correct Answer: A
Rationale: Schwann cells are indeed responsible for producing the myelin sheath in the peripheral nervous system. These cells wrap around axons to form the myelin sheath, which enhances the speed of nerve impulse conduction. In the central nervous system, oligodendrocytes are responsible for producing the myelin sheath. Astrocytes provide support and maintenance functions for neurons, while neurons are the nerve cells themselves and do not produce myelin. Therefore, the correct answer is Schwann cells as they are specifically involved in myelin production in the peripheral nervous system.
Diabetic nephropathy, a complication of diabetes, affects the:
- A. Ureters
- B. Bladder
- C. Urethra
- D. Nephrons
Correct Answer: D
Rationale: Diabetic nephropathy, a complication of diabetes, affects the nephrons. Nephrons are the functional units of the kidneys responsible for filtering blood and producing urine. The high blood sugar levels associated with diabetes can damage the nephrons over time, leading to kidney dysfunction and, ultimately, kidney failure. Choices A, B, and C are incorrect because diabetic nephropathy primarily impacts the nephrons in the kidneys, not the ureters, bladder, or urethra.
What is the name of the wart-like growths caused by the human papillomavirus (HPV)?
- A. Keloids
- B. Keloids
- C. Papillomas
- D. Carcinomas
Correct Answer: C
Rationale: The correct answer is 'Papillomas.' Papillomas are benign wart-like growths caused by the human papillomavirus (HPV). Keloids are raised scars that occur at the site of an injury due to excessive collagen formation, while carcinomas are malignant tumors arising from epithelial cells. When identifying the growths specifically related to HPV, papillomas are the most appropriate term.