HESI A2
HESI A2 Chemistry Practice Test
1. Which type of radiation emits helium ions and can be stopped by a piece of paper?
- A. Beta radiation
- B. Alpha radiation
- C. Gamma radiation
- D. X-ray radiation
Correct answer: B
Rationale: Alpha radiation emits helium ions, which are helium nuclei without electrons, making them positively charged. These ions are relatively large and heavy compared to beta and gamma radiation. Due to their size and charge, alpha particles interact strongly with matter and are easily stopped. A piece of paper or even human skin can effectively block alpha radiation. Therefore, alpha radiation is the type of radiation that can be stopped by a piece of paper. Beta radiation consists of fast-moving electrons and can penetrate further into materials than alpha radiation, thus not stopped by a piece of paper. Gamma radiation is highly penetrating and requires dense materials like lead or concrete to block it effectively. X-ray radiation, similar to gamma radiation, is also highly penetrating and cannot be stopped by a piece of paper.
2. What is the correct formula for silver hydroxide?
- A. AgO
- B. AgOH
- C. AgH
- D. AgH₂O
Correct answer: B
Rationale: The correct formula for silver hydroxide is AgOH. Silver hydroxide is formed by the combination of the silver ion (Ag⁺) with the hydroxide ion (OH⁻) to create AgOH. It is essential to note that the hydroxide ion consists of one oxygen and one hydrogen atom, thus the formula AgOH. Choices A, C, and D are incorrect as they do not accurately represent the composition of silver hydroxide.
3. Which type of chemical reaction involves an active metal reacting with an ionic compound to create a new compound?
- A. Combustion
- B. Single replacement
- C. Synthesis
- D. Decomposition
Correct answer: B
Rationale: The correct answer is 'Single replacement.' In a single replacement reaction, an active metal replaces another element in an ionic compound, resulting in the formation of a new compound. Option A, 'Combustion,' involves a substance rapidly reacting with oxygen to release energy in the form of heat and light. Option C, 'Synthesis,' involves the combination of two or more substances to form a more complex product. Option D, 'Decomposition,' involves the breakdown of a compound into simpler substances.
4. What is a benefit of water's ability to make hydrogen bonds?
- A. Lack of cohesiveness
- B. Low surface tension
- C. Use as a nonpolar solvent
- D. High specific heat
Correct answer: D
Rationale: The correct answer is D, high specific heat. Water's ability to form hydrogen bonds results in a high specific heat capacity, allowing it to absorb and release a large amount of heat energy with minimal temperature change. This property is essential for moderating temperature changes in organisms and maintaining stable environmental conditions for life processes. Choices A, lack of cohesiveness, and C, use as a nonpolar solvent, are incorrect. Water actually has high cohesiveness due to its ability to form hydrogen bonds, and it is a polar solvent, not nonpolar. Choice B, low surface tension, is also incorrect as water's hydrogen bonding contributes to its relatively high surface tension.
5. Which gas is produced when an acid reacts with a carbonate?
- A. Carbon dioxide
- B. Oxygen
- C. Hydrogen
- D. Nitrogen
Correct answer: A
Rationale: When an acid reacts with a carbonate, the chemical reaction typically yields carbon dioxide gas. Carbon dioxide is formed due to the chemical reaction between the acid and the carbonate, releasing this gas as a product. Therefore, the correct answer is 'Carbon dioxide.' Choices B, C, and D are incorrect as oxygen, hydrogen, and nitrogen are not the gases produced in this specific acid-carbonate reaction.
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