HESI A2
Chemistry HESI A2 Quizlet
1. What type of chemical reaction involves the reaction of a compound with oxygen?
- A. Decomposition
- B. Synthesis
- C. Combustion
- D. Single replacement
Correct answer: C
Rationale: The correct answer is C: Combustion. A combustion reaction is characterized by a compound reacting with oxygen. During this process, heat and light are often produced as energy is released in the form of heat. Combustion is a common type of reaction involving organic compounds, like hydrocarbons, reacting with oxygen to produce carbon dioxide and water. Choices A, B, and D are incorrect because decomposition involves a compound breaking down into simpler substances, synthesis involves the combination of two or more substances to form a more complex one, and single replacement involves an element replacing another element in a compound.
2. How many electrons are shared in a single covalent bond?
- A. 1
- B. 2
- C. 3
- D. 4
Correct answer: B
Rationale: The correct answer is B: '2'. In a single covalent bond, two electrons are shared between two atoms. Each atom contributes one electron to form the bond, resulting in the sharing of a total of two electrons. Choice A is incorrect because a single covalent bond involves the sharing of two electrons, not one. Choices C and D are incorrect as they do not represent the correct number of electrons shared in a single covalent bond.
3. How can water be boiled at room temperature?
- A. By lowering the pressure
- B. By increasing the pressure
- C. By decreasing the volume
- D. By raising the boiling point
Correct answer: A
Rationale: The boiling point of water is directly affected by pressure. By lowering the pressure, water can boil at a lower temperature, even at room temperature. This occurs because at lower pressures, the molecules of water have less resistance to escaping into the vapor phase, thus enabling boiling to occur at lower temperatures. Choices B, C, and D are incorrect because increasing the pressure, decreasing the volume, or raising the boiling point would actually require higher temperatures to boil water rather than achieving boiling at room temperature.
4. You contain two odorous gases in vials with porous plugs. Gas A has twice the mass of Gas B. Which observation is most likely?
- A. You will smell Gas A before you smell Gas B.
- B. You will smell Gas B before you smell Gas A.
- C. You will smell Gas A but not Gas B.
- D. You will smell Gas B but not Gas A.
Correct answer: A
Rationale: The rate of effusion of a gas is inversely proportional to the square root of its molar mass. Since Gas A has twice the mass of Gas B, Gas A will effuse more slowly than Gas B. Therefore, you will likely smell Gas A before you smell Gas B as Gas A will escape and diffuse through the porous plug at a slower rate compared to Gas B. Choice A is correct because Gas A, with its higher molar mass, will take longer to effuse through the porous plug, causing you to smell it first. Choices B, C, and D are incorrect as they do not consider the relationship between molar mass and effusion rate.
5. What are the 3 types of radiation in nuclear chemistry?
- A. Alpha, Beta, Delta
- B. Alpha, Beta, Gamma
- C. Gamma, Beta, Delta
- D. Delta, Beta, Gamma
Correct answer: B
Rationale: The correct answer is B: Alpha, Beta, Gamma. In nuclear chemistry, the 3 types of radiation are alpha, beta, and gamma radiation. Alpha radiation consists of helium nuclei, beta radiation involves electrons or positrons, and gamma radiation is electromagnetic radiation of high frequency. Choice A is incorrect because 'Delta' is not a type of radiation in nuclear chemistry. Choice C is incorrect as it does not list alpha radiation. Choice D is incorrect as it lists the types in the wrong order and includes 'Delta' instead of alpha radiation.
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