Nokea
An uncharged atom has an electron configuration of 1s² 2s² 2pⶠ3s² and a mass number of 14. How many protons does it have?
- A. 14
- B. 6
- C. 8
- D. 12
Correct Answer: B
Rationale: The number of protons in an atom is determined by the atomic number, which is equal to the number of protons in the nucleus. The electron configuration given corresponds to carbon (C) with 6 protons. The atomic number of an element is the same as the number of protons in its nucleus, so in this case, the atom has 6 protons. Choices A, C, and D are incorrect because they do not correspond to the correct number of protons for an atom with the given electron configuration and mass number. Therefore, option B, 6 protons, is the correct answer.
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What is the term for the gradual loss of topsoil due to wind or water erosion?
- A. Desertification
- B. Leaching
- C. Salinization
- D. Acidification
Correct Answer: A
Rationale: A) Desertification is the correct term for the gradual loss of topsoil due to wind or water erosion. It refers to the process by which fertile land becomes desert, usually due to factors like drought, deforestation, or inappropriate agriculture practices. This process can lead to the degradation of land and contribute to the expansion of deserts. B) Leaching is the process in which minerals are washed out of the soil by water moving downwards through it. This is different from the loss of topsoil due to erosion. C) Salinization occurs when salt accumulates in the soil, typically as a result of irrigation in arid regions. While salinization affects soil quality, it is not specifically related to the gradual loss of topsoil due to erosion. D) Acidification refers to the decrease in soil pH, often caused by factors like acid rain or the use of acidic fertilizers. This process is distinct from the gradual loss of topsoil due to erosion.
In which group of the periodic table are alkali metals located?
- A. Group 1
- B. Group 2
- C. Group 7
- D. Group 8
Correct Answer: A
Rationale: Alkali metals, such as lithium, sodium, and potassium, are located in Group 1 of the periodic table. This group is known for its highly reactive properties, low melting points, and the tendency to form alkaline solutions when they react with water. Group 2 consists of alkaline earth metals and not alkali metals, making choice B incorrect. Group 7 includes halogens, while Group 8 includes noble gases. These groups do not contain alkali metals, so choices C and D are also incorrect. Therefore, the correct answer is Group 1.
What is the acceleration of an object moving at a constant speed of 20 m/s if it comes to a complete stop within 5 seconds?
- A. 0 m/s² (no acceleration)
- B. 4 m/s²
- C. -4 m/s²
- D. Insufficient information
Correct Answer: C
Rationale: To find the acceleration, we use the formula: acceleration = (final velocity - initial velocity) / time. Given that the final velocity is 0 m/s (as the object stops), the initial velocity is 20 m/s, and the time taken is 5 seconds. Substituting these values into the formula, we get acceleration = (0 m/s - 20 m/s) / 5 s = -20 m/s / 5 s = -4 m/s². Therefore, the acceleration is -4 m/s², indicating that the object decelerated at a rate of 4 m/s² to come to a complete stop. Choice A is incorrect because the object does experience acceleration as it changes its speed from 20 m/s to 0 m/s. Choice B is incorrect as it represents acceleration in the wrong direction, considering the object is decelerating. Choice D is incorrect as there is sufficient information provided to calculate the acceleration based on the given data.
Which hormone is produced by the thyroid gland to regulate metabolism?
- A. Adrenaline
- B. Thyroxine
- C. Cortisol
- D. Insulin
Correct Answer: B
Rationale: Thyroxine, also known as T4, is the hormone produced by the thyroid gland to regulate metabolism. It is essential for controlling the body's metabolic rate, heart and digestive function, muscle control, brain development, and bone maintenance. Adrenaline is produced by the adrenal glands, not the thyroid gland. Cortisol is produced by the adrenal cortex, not the thyroid gland. Insulin is produced by the pancreas, not the thyroid gland. Therefore, the correct answer is Thyroxine (B).
Which respiratory structure is responsible for the humidification and warming of inhaled air?
- A. Trachea
- B. Larynx
- C. Nasal passages
- D. Bronchi
Correct Answer: C
Rationale: The nasal passages are responsible for humidifying and warming inhaled air before it reaches the lungs. The mucous membranes in the nasal passages help add moisture to the air and warm it to body temperature. This process is crucial for protecting the lung tissues from potential damage caused by cold and dry air, ensuring optimal conditions for respiration. The trachea (Choice A) is responsible for conducting air to and from the lungs, the larynx (Choice B) is involved in sound production and protecting the airway during swallowing, and the bronchi (Choice D) are the branches of the trachea that further divide to deliver air to the lungs but are not primarily responsible for humidifying and warming inhaled air.