which chemical reaction involves the breaking of a compound into its components
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HESI A2

HESI A2 Chemistry Questions

1. Which chemical reaction involves the breaking of a compound into its components?

Correct answer: A

Rationale: The correct answer is A: Decomposition reaction. A decomposition reaction involves breaking down a compound into its components. During this reaction, a single compound breaks down into two or more simpler substances. This process is the opposite of a synthesis reaction where multiple substances combine to form a more complex compound. Choices B, C, and D are incorrect because combustion reaction involves burning a substance in oxygen, neutralization reaction involves the reaction between an acid and a base to form water and a salt, and single displacement reaction involves an element displacing another in a compound.

2. A salt solution has a molarity of 5 M. How many moles of this salt are present in 0 L of this solution?

Correct answer: A

Rationale: Molarity is defined as the number of moles of solute per liter of solution. A molarity of 5 M indicates there are 5 moles of salt in 1 liter of the solution. Since the volume of the solution is 0 liters, multiplying the molarity by 0 liters results in 0 moles of salt (5 moles/L x 0 L = 0 moles). Therefore, the correct answer is 0. Option B, 1.5, is incorrect because it doesn't consider the volume being 0 liters. Options C and D, 2 and 3 respectively, are also incorrect as they do not account for the zero volume of the solution. Hence, there are no moles of salt present in 0 liters of the solution.

3. What is the normal body temperature in °C?

Correct answer: B

Rationale: The normal body temperature for humans is 37°C. This temperature is considered average and is a standard reference point for assessing an individual's health status. It is essential for the body to maintain this temperature to ensure optimal functioning of various physiological processes. Choice A (36°C) is incorrect as it is slightly below the normal body temperature. Choice C (35°C) is also incorrect as it is significantly lower than the normal body temperature. Choice D (40°C) is incorrect as it is significantly higher than the normal body temperature and would indicate a fever or other health issue.

4. Which compound is a Hydrogen or proton donor, corrosive to metals, causes blue litmus paper to become red, and becomes less acidic when mixed with a base?

Correct answer: B

Rationale: The correct answer is 'Acid.' An acid is a compound that donates protons (H+), is corrosive to metals, and turns blue litmus paper red. When an acid is mixed with a base, they react to form salts and water, resulting in a decrease in acidity. Choices A, C, and D are incorrect because bases accept protons rather than donate them, salts are the products of acid-base reactions, and hydroxides are typically bases, not acids.

5. What is the name of the negatively charged subatomic particles?

Correct answer: C

Rationale: The correct answer is C: Electrons. Electrons are the negatively charged subatomic particles. They are found outside the atomic nucleus and carry a negative charge. Protons are positively charged particles found in the nucleus, neutrons have no charge, and isotopes are atoms of the same element with different numbers of neutrons, not subatomic particles.

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