HESI A2
HESI A2 Chemistry Questions
1. What is the name for the horizontal rows of the periodic table?
- A. groups
- B. periods
- C. families
- D. sets
Correct answer: B
Rationale: In the periodic table, 'periods' are the horizontal rows. Each period corresponds to the energy level occupied by the elements in that row. The other terms mentioned, such as groups, families, and sets, are not used to describe the horizontal rows but rather refer to different aspects of the periodic table organization. 'Groups' are the vertical columns, 'families' are groups of elements with similar properties, and 'sets' is a more generic term not specifically used in the context of the periodic table.
2. What are positively charged ions called?
- A. Neutrons
- B. Protons
- C. Cations
- D. Electrons
Correct answer: C
Rationale: Positively charged ions are called cations. When an atom loses electrons, it becomes positively charged and is referred to as a cation. Neutrons are neutral particles found in the nucleus of an atom, not charged. Protons are positively charged particles in the nucleus. Electrons are negatively charged particles orbiting the nucleus, not positively charged ions.
3. What is the primary function of enzymes?
- A. To provide energy for reactions
- B. To speed up reactions
- C. To decrease activation energy
- D. To act as a catalyst
Correct answer: B
Rationale: Enzymes function to speed up reactions by lowering the activation energy required for the reaction to occur. They act as biological catalysts, providing an alternative pathway for the reaction to proceed more rapidly without being consumed in the process. Choices A, C, and D are incorrect because enzymes do not provide energy for reactions (they do not generate energy), their primary function is not to decrease activation energy (though they do lower it), and while they act as catalysts, the primary function is to speed up reactions by lowering activation energy.
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 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.
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