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. What charge do alpha radiation particles have?
- A. -2
- B. 0
- C. +2
- D. +1
Correct answer: C
Rationale: The correct answer is C: +2. Alpha radiation particles consist of two protons and two neutrons, giving them a net charge of +2. This positive charge is due to the presence of the two protons in the nucleus of the alpha particle. Choice A (-2) is incorrect as alpha particles have a positive charge. Choice B (0) is incorrect as alpha particles carry a charge. Choice D (+1) is incorrect as alpha particles have a higher positive charge due to the presence of two protons.
3. How does increasing the concentration of reactants affect a chemical reaction?
- A. Decreases the reaction rate
- B. Increases the reaction rate
- C. Stops the reaction
- D. Has no effect
Correct answer: B
Rationale: Increasing the concentration of reactants leads to more reactant particles being available, which, in turn, increases the likelihood of successful collisions between particles. This higher frequency of collisions results in a higher reaction rate. Therefore, option B, 'Increases the reaction rate,' is the correct answer. Choice A, 'Decreases the reaction rate,' is incorrect because higher reactant concentration usually speeds up the reaction. Choice C, 'Stops the reaction,' is incorrect as increasing concentration promotes more collisions, enhancing the reaction. Choice D, 'Has no effect,' is incorrect because changing reactant concentration directly impacts the reaction rate in most cases.
4. What type of reaction involves atoms attempting to achieve stable electron configurations?
- A. Chemical
- B. Nuclear
- C. Physical
- D. Mechanical
Correct answer: A
Rationale: In a chemical reaction, atoms interact to achieve stable electron configurations through the formation of new chemical bonds or the breaking of existing ones. This process aims to reach a more stable state by filling or emptying electron orbitals, leading to the formation of new substances with more stable configurations. Choice B, nuclear reactions, involve changes in the atomic nucleus rather than electron configurations. Choice C, physical reactions, involve changes in physical state or appearance without changing the chemical makeup. Choice D, mechanical reactions, do not involve the rearrangement of electrons to achieve stable configurations.
5. What color does phenolphthalein turn in the presence of an acid?
- A. Clear
- B. Blue
- C. Pink
- D. Red
Correct answer: C
Rationale: In the presence of an acid, phenolphthalein turns pink. Phenolphthalein is a pH indicator that is colorless in acidic solutions but turns pink in basic solutions. Therefore, when added to an acidic solution, phenolphthalein will exhibit a pink coloration. Choice A, 'Clear,' is incorrect because phenolphthalein does not remain colorless in the presence of an acid. Choice B, 'Blue,' is incorrect as phenolphthalein does not turn blue in the presence of an acid. Choice D, 'Red,' is incorrect as phenolphthalein does not exhibit a red color in acidic solutions.
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