HESI A2
HESI A2 Chemistry
1. What is a pentose sugar?
- A. A 6 carbon sugar
- B. A 4 carbon sugar
- C. A 5 carbon sugar
- D. A 7 carbon sugar
Correct answer: C
Rationale: A pentose is a 5-carbon sugar, as the prefix 'pent-' signifies five. Therefore, a pentose sugar consists of five carbon atoms. Choice A, 'A 6 carbon sugar,' is incorrect as a pentose sugar specifically has five carbons. Choice B, 'A 4 carbon sugar,' is incorrect as it describes a tetrose sugar, which has four carbons. Choice D, 'A 7 carbon sugar,' is incorrect as it does not correspond to the definition of a pentose sugar.
2. Which of the following is a characteristic property of acids?
- A. Sour taste
- B. Bitter taste
- C. Reacts with bases
- D. Slippery feel
Correct answer: A
Rationale: The correct answer is 'A: Sour taste.' Acids are known to have a sour taste, which is a fundamental characteristic property of acids. This taste distinguishes acids from bases, which are more likely to have a bitter taste. The sour taste of acids is due to the presence of hydrogen ions in them. Therefore, when identifying an acid based on taste, the sour taste serves as a key indicator. Choices B, C, and D are incorrect. Bitter taste is associated with bases, not acids. While acids do react with bases (Choice C), this is not a characteristic property of acids but rather a chemical behavior. Slippery feel (Choice D) is a property of bases, not acids.
3. What is the coefficient of O after the following equation is balanced?
- A. 1
- B. 2
- C. 3
- D. 4
Correct answer: A
Rationale: In a balanced chemical equation, the coefficient of oxygen (O) in O2 is already 2, so there is no need to adjust its coefficient further. Therefore, the coefficient of O remains as 1. Since the coefficient of O2 is 2, each O atom is represented by the coefficient of 1, and it does not change during the balancing process. Choices B, C, and D are incorrect as they suggest changing the coefficient of oxygen, which is not necessary for O2 in a balanced equation.
4. What is the product of the decomposition of water?
- A. Hydrogen and oxygen
- B. Carbon dioxide
- C. Nitrogen and hydrogen
- D. Methane
Correct answer: A
Rationale: The correct answer is A: Hydrogen and oxygen. When water undergoes decomposition, it breaks down into hydrogen and oxygen gases through a process known as electrolysis. This reaction is represented by 2H₂O → 2H₂ + O₂. Choice B, carbon dioxide, is incorrect as it is not a product of water decomposition. Choice C, nitrogen and hydrogen, is incorrect as water decomposes into hydrogen and oxygen, not nitrogen. Choice D, methane, is incorrect as methane is not a product of water decomposition.
5. Which type of radiation involves the emission of helium ions?
- A. Beta
- B. Alpha
- C. Gamma
- D. Delta
Correct answer: B
Rationale: Alpha radiation involves the emission of helium ions. Helium ions are composed of two protons and two neutrons, which is the same as the nucleus of a helium atom. This type of radiation has low penetration power and can be stopped by a piece of paper or human skin, making it less harmful compared to other forms of radiation like beta or gamma radiation. Beta radiation involves the emission of high-speed electrons, while gamma radiation involves electromagnetic waves with high energy. Delta radiation is not a recognized form of radiation in this context, making it an incorrect choice.
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