Nokea
What is the pH value of a neutral solution?
- B. 7
- C. 14
- D. -7
Correct Answer: B
Rationale: The pH scale measures the acidity or basicity of a solution. A pH of 7 is considered neutral, indicating that the concentration of hydrogen ions (H+) is equal to the concentration of hydroxide ions (OH-) in the solution. A pH ranging from 0 to 6.9 signifies acidity, while a pH from 7.1 to 14 signifies alkalinity. Therefore, a neutral solution has a pH value of 7. Choice A (0) represents a highly acidic solution, Choices C (14) and D (-7) are outside the valid pH range and do not correspond to a neutral solution.
You may also like to solve these questions
What is the term for a substance that can act as both a proton donor and a proton acceptor?
- A. Acid
- B. Base
- C. Amphiprotic
- D. Neutral
Correct Answer: C
Rationale: Amphiprotic substances are those that can both donate and accept protons. They possess characteristics of both acids and bases, making them capable of acting as proton donors and proton acceptors. Choices A and B represent substances that are specific to either donating or accepting protons. Choice D does not describe a substance's ability to donate or accept protons since neutrality does not inherently involve proton donation or acceptance.
In physics, what does the term 'terminal velocity' refer to?
- A. Maximum velocity reached by an object in free fall
- B. Velocity when the object is at rest
- C. Instantaneous velocity of an object
- D. Velocity only reached by heavy objects
Correct Answer: A
Rationale: Terminal velocity in physics refers to the maximum velocity achieved by an object in free fall when the force of gravity equals the force of air resistance. At terminal velocity, the object stops accelerating and maintains a constant speed. This occurs when the opposing forces are balanced, leading to no further increase in speed. Choice B is incorrect as velocity when the object is at rest is zero, not at terminal velocity. Choice C is incorrect as instantaneous velocity refers to the velocity at a specific moment in time, not the maximum speed reached in free fall. Choice D is incorrect because terminal velocity is not exclusive to heavy objects; all objects in free fall can reach terminal velocity under the right conditions.
What property of a wave determines its pitch in sound waves?
- A. Amplitude
- B. Frequency
- C. Wavelength
- D. Speed
Correct Answer: B
Rationale: The pitch of a sound wave is determined by its frequency. Frequency is the number of cycles of a wave that occur in a unit of time, usually measured in hertz (Hz). Higher frequencies correspond to higher pitches, while lower frequencies correspond to lower pitches. Amplitude refers to the height of a wave and is related to the loudness of the sound. Wavelength is the distance between two consecutive points in a wave that are in phase, and speed is the rate at which a wave travels through a medium. Therefore, the correct answer is frequency as it directly correlates with the pitch of a sound wave.
What does the innate immune system provide?
- A. Nonspecific, immediate defense against pathogens
- B. Specific, long-term immune response through memory cells
- C. Both (a) and (b)
- D. Neither (a) nor (b)
Correct Answer: A
Rationale: The correct answer is A. The innate immune system provides nonspecific, immediate defense against pathogens. It is the body's first line of defense in responding to infections and does not involve memory cells or specific long-term immune responses like the adaptive immune system. Choice B is incorrect because specific, long-term immune responses through memory cells are characteristics of the adaptive immune system, not the innate immune system. Choice C is incorrect because the innate immune system does not provide specific, long-term immune responses. Choice D is incorrect because the innate immune system does provide an immediate defense against pathogens.
Which of the following is a characteristic of alkenes?
- A. They have a double bond between carbon atoms.
- B. They are saturated hydrocarbons.
- C. They contain only single bonds.
- D. They are derivatives of ammonia.
Correct Answer: A
Rationale: Alkenes are hydrocarbons that contain at least one carbon-carbon double bond. This double bond is a key characteristic that distinguishes alkenes from other types of hydrocarbons. Option A correctly identifies this defining feature of alkenes, making it the correct answer. Choices B, C, and D are incorrect. Choice B is incorrect because alkenes are unsaturated hydrocarbons due to the presence of double bonds. Choice C is incorrect as alkenes do not contain only single bonds; they have at least one double bond. Choice D is incorrect because alkenes are not derivatives of ammonia; they are a distinct class of organic compounds with carbon-carbon double bonds.