HESI A2 Chemistry Questions

Correct Answer: A

Rationale: The correct answer is A: Synthesis reaction. In a synthesis reaction, two or more reactants combine to form a single product. This type of reaction is characterized by the formation of a more complex molecule from simpler ones. The other choices are incorrect because: B: Combustion reaction involves the rapid combination of a substance with oxygen, producing heat and light. C: Decomposition reaction involves the breakdown of a compound into simpler substances. D: Double displacement reaction involves the exchange of ions between two compounds to form two new compounds.

Correct Answer: B

Rationale: The correct answer is B: Iron. The chemical symbol 'Fe' represents the element iron in the periodic table. Iron is a transition metal with atomic number 26. It is commonly used in construction, manufacturing, and as a vital nutrient in the human body. Lead (choice A), Silver (choice C), and Copper (choice D) have the chemical symbols 'Pb', 'Ag', and 'Cu' respectively, making them incorrect choices. By knowing the periodic table and corresponding chemical symbols, we can easily identify the correct element.

Correct Answer: A

Rationale: The correct answer is A: Fluorine. Fluorine has the highest electronegativity because it has the smallest atomic size among the choices, leading to a stronger attraction for electrons. This makes it more likely to attract electrons in a chemical bond. Chlorine, Nitrogen, and Oxygen have lower electronegativities compared to Fluorine due to their larger atomic sizes, resulting in weaker electron-attracting capabilities. Remember, electronegativity generally increases across a period from left to right in the periodic table.

Correct Answer: B

Rationale: The correct answer is B: Nitrogen. Nitrogen makes up about 78% of Earth's atmosphere, making it the main component of air. Oxygen (A) is the second most abundant gas in the atmosphere at around 21%. Carbon dioxide (C) is present in much lower concentrations, around 0.04%. Argon (D) is also a minor component of air, at less than 1%. Nitrogen's high percentage in the atmosphere is the reason it is considered the main component of air.

Correct Answer: A

Rationale: The correct answer is A: Synthesis reaction. In a synthesis reaction, two or more reactants combine to form a single product. This type of reaction is characterized by the formation of a more complex molecule from simpler ones. The other choices are incorrect because: B: Combustion reaction involves the rapid combination of a substance with oxygen, producing heat and light. C: Decomposition reaction involves the breakdown of a compound into simpler substances. D: Double displacement reaction involves the exchange of ions between two compounds to form two new compounds.