HESI A2
HESI A2 Chemistry Questions
1. What type of reaction occurs when an acid and a base react to form water and salt?
- A. Neutralization reaction
- B. Decomposition reaction
- C. Combustion reaction
- D. Redox reaction
Correct answer: A
Rationale: A neutralization reaction is the correct answer. In this type of reaction, an acid and a base combine to form water and salt. The acid donates a proton (H+) to the base, forming water, while the remaining ions combine to form a salt. This reaction results in the neutralization of both the acid and the base, hence the name 'neutralization reaction.' Choice B, decomposition reaction, is incorrect because it refers to a reaction where a compound breaks down into simpler substances. Choice C, combustion reaction, is incorrect as it involves a substance reacting with oxygen to produce heat and light. Choice D, redox reaction, is incorrect because it involves the transfer of electrons between reactants.
2. What is an alloy in which another metal is dissolved in mercury (Hg) called?
- A. Electrum
- B. Amalgam
- C. Solder
- D. Bronze
Correct answer: B
Rationale: An amalgam is a type of alloy where another metal is dissolved in mercury (Hg). This process forms a unique mixture that has various applications in dentistry, chemistry, and other fields. Electrum is a natural alloy of gold and silver, solder is a metal alloy used to join other metals together, and bronze is a copper-tin alloy. Therefore, the correct answer is B - Amalgam.
3. Which ion would you expect to dominate in water solutions of bases?
- A. MgClâ‚‚
- B. 2HCl
- C. Hâº
- D. OHâ»
Correct answer: D
Rationale: In water solutions of bases, the dominant ion would be OH⻠(hydroxide ion). Bases release OH⻠ions when dissolved in water, increasing the concentration of hydroxide ions and leading to a higher pH. This is in contrast to acids, which release H⺠ions. Therefore, in water solutions of bases, the presence of OH⻠ions signifies the basic nature of the solution. Choices A, B, and C are incorrect because MgCl₂ is a salt, 2HCl is a compound consisting of two hydrogen ions and one chloride ion, and H⺠represents a hydrogen ion typically associated with acids, not bases.
4. How many electron pairs are shared to form a double covalent bond?
- A. 1
- B. 2
- C. 3
- D. 4
Correct answer: B
Rationale: The correct answer is B. In a double covalent bond, two pairs of electrons are shared between two atoms. This sharing of two electron pairs results in a stronger bond compared to a single covalent bond where only one pair of electrons is shared. Choice A is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choices C and D are incorrect as they do not represent the correct number of electron pairs shared in a double covalent bond.
5. 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.
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