Nokea
Which of the following substances can donate a hydroxide ion (OH-) in solution?
- A. Salt
- B. Base
- C. Neutral compound
- D. Dehydrating agent
Correct Answer: B
Rationale: The correct answer is B: Base. A base is a substance that can donate hydroxide ions (OH-) in solution. Bases increase the concentration of hydroxide ions by either accepting protons (H+) or donating hydroxide ions. Salts are ionic compounds made of cations and anions, which do not directly donate hydroxide ions. Neutral compounds do not significantly affect the concentration of hydroxide ions. Dehydrating agents are substances that remove water molecules from other compounds, unrelated to donating hydroxide ions.
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Which hormone, produced by the adrenal glands, helps regulate the body's response to stress, including increasing blood pressure and suppressing the immune system?
- A. Aldosterone
- B. Epinephrine
- C. Cortisol
- D. Insulin
Correct Answer: C
Rationale: Cortisol is the correct answer. It is the hormone produced by the adrenal glands that helps regulate the body's response to stress. Cortisol plays a crucial role in increasing blood pressure and suppressing the immune system during stressful situations. Aldosterone, another hormone from the adrenal glands, primarily regulates salt and water balance in the body, not the stress response. Epinephrine, also known as adrenaline, is produced by the adrenal glands in response to stress, but its effects are more immediate and short-lived compared to cortisol. Insulin, produced by the pancreas, regulates blood sugar levels and is not directly involved in the body's response to stress.
When baking soda (sodium bicarbonate) reacts with vinegar (acetic acid), what type of reaction occurs?
- A. Combustion
- B. Double displacement
- C. Decomposition
- D. Synthesis
Correct Answer: B
Rationale: When baking soda (sodium bicarbonate) reacts with vinegar (acetic acid), a double displacement reaction occurs. In this reaction, the positive ions in baking soda switch places with the positive ions in vinegar to form water, carbon dioxide, and a salt. Combustion involves a reaction with oxygen to produce heat and light energy. Decomposition is the breakdown of a compound into simpler substances, which is not the case in the given reaction. Synthesis is the combination of substances to form a more complex compound, which is also not the type of reaction observed when baking soda and vinegar react.
Imagine you have an element with atomic number 20 and mass number 40. How many neutrons does it have?
- A. 20
- B. 40
- C. 10
- D. 20
Correct Answer: C
Rationale: - The atomic number (Z) represents the number of protons in an atom. In this case, the atomic number is 20.
- The mass number (A) represents the total number of protons and neutrons in an atom. In this case, the mass number is 40.
- To find the number of neutrons, you subtract the atomic number from the mass number: Neutrons = Mass number - Atomic number.
- Neutrons = 40 - 20 = 20.
- Therefore, the element with atomic number 20 and mass number 40 has 20 neutrons.
Which structure in the respiratory system serves as a passageway for both air and food, with a flap-like structure that prevents food from entering the trachea during swallowing?
- A. Larynx
- B. Pharynx
- C. Trachea
- D. Bronchi
Correct Answer: B
Rationale: The pharynx is the correct answer. The pharynx is a structure in the respiratory system that serves as a passageway for both air and food. It contains a flap-like structure called the epiglottis, which prevents food from entering the trachea during swallowing by covering the opening to the trachea. The larynx, although important in the respiratory system, is located below the pharynx and contains the vocal cords. The trachea is a tube that carries air to and from the lungs, while the bronchi are the two main branches that lead from the trachea into the lungs.
In a food chain, which trophic level captures energy from the sun?
- A. Decomposers
- B. Carnivores
- C. Producers
- D. Omnivores
Correct Answer: C
Rationale: Producers, such as plants, algae, and some bacteria, are the organisms in a food chain that capture energy from the sun through the process of photosynthesis. They convert sunlight into chemical energy, which is then passed on to other organisms in the food chain. Producers are at the base of the food chain and form the foundation for all other trophic levels to obtain energy. Decomposers (option A) break down organic matter, carnivores (option B) consume other animals, and omnivores (option D) consume both plants and animals, but they do not directly capture energy from the sun.