which of the following is a characteristic of an exothermic reaction
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HESI A2

HESI A2 Chemistry Questions

1. Which of the following is a characteristic of an exothermic reaction?

Correct answer: B

Rationale: An exothermic reaction is characterized by the release of heat. During an exothermic reaction, energy is released in the form of heat to the surroundings, resulting in a temperature increase. This distinguishes it from endothermic reactions, which absorb heat from the surroundings. Choice A is incorrect because exothermic reactions do not absorb heat; instead, they release heat. Choice C is incorrect as exothermic reactions do not remain neutral; they involve a net release of energy. Choice D is incorrect as exothermic reactions do not require energy input; instead, they release energy.

2. What form of radiation is composed of electrons traveling at around 16,000 km/sec?

Correct answer: B

Rationale: Beta radiation is composed of high-energy electrons (β- particles) or positrons (β+ particles) traveling at considerable speeds. In this case, the electrons traveling at around 16,000 km/sec align with the characteristics of beta radiation, making it the correct choice. Alpha radiation consists of helium nuclei, gamma radiation is electromagnetic radiation of high frequency, and delta radiation is not a recognized form of radiation, making them all incorrect choices.

3. Which gas is released during photosynthesis?

Correct answer: B

Rationale: During photosynthesis, plants utilize carbon dioxide and water to produce glucose and oxygen. Oxygen is released as a byproduct of this process, which is essential for the survival of most living organisms that depend on it for respiration. Therefore, the correct answer is oxygen. Choices A, C, and D are incorrect. Carbon dioxide is utilized in photosynthesis, nitrogen is not directly involved in the process, and helium is not a gas released during photosynthesis.

4. On what concept is Kelvin based?

Correct answer: B

Rationale: The correct answer is B: Absolute zero. Kelvin is based on the concept of absolute zero, which is the point where molecular movement ceases entirely. This temperature scale starts at absolute zero (0K), where theoretically no molecular movement occurs. Choices A, C, and D are incorrect because Kelvin is not based on the freezing point, boiling point, or evaporation point, but rather on the absolute absence of molecular motion.

5. What charge do Group IIA elements typically have?

Correct answer: B

Rationale: Group IIA elements belong to the alkaline earth metals group in the periodic table. These elements typically have a charge of +2 because they readily lose two electrons to achieve a stable electron configuration. Therefore, the correct answer is B - +2. Choice A (1) is incorrect because Group IIA elements lose two electrons, not one. Choice C (-3) is incorrect because Group IIA elements do not gain electrons to have a negative charge. Choice D (0) is incorrect because Group IIA elements do lose electrons and have a positive charge, not a neutral charge.

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