HESI A2 Chemistry

Correct Answer: C

Rationale: The correct balanced equation is 2Fe + O₂ → 2FeO. This is because there is 1 Fe atom on each side, 2 O atoms on each side, and the ratio of Fe to O is 2:2. Choice A has incorrect coefficients for Fe and O, choice B has an incorrect ratio of Fe to O, and choice D also has incorrect coefficients for Fe and O. Thus, the correct answer is C as it maintains the balance of atoms on both sides of the equation.

Correct Answer: B

Rationale: The correct answer is B: Alpha, Beta, Gamma. - Alpha radiation consists of helium nuclei. - Beta radiation consists of high-energy electrons or positrons. - Gamma radiation is electromagnetic radiation. Alpha, Beta, and Gamma are the three most common types of radiation in nuclear chemistry. Choice A is incorrect because "Delta" is not a type of radiation in nuclear chemistry. Choice C is incorrect because "Delta" is not a type of radiation, and the order is incorrect. Choice D is incorrect because "Delta" is not a type of radiation, and the order is incorrect.

Correct Answer: C

Rationale: The correct answer is C: A 5 carbon sugar. Pentose sugars are carbohydrates with 5 carbon atoms. They are essential components of nucleic acids like DNA and RNA. A is incorrect because it has 6 carbons, not 5. B is incorrect as it has 4 carbons. D is incorrect as it has 7 carbons, not 5. Therefore, the correct choice is C as it accurately describes a pentose sugar.

Correct Answer: D

Rationale: The correct answer is D, H₂O. Water (H₂O) contains a polar covalent bond. This is because oxygen is more electronegative than hydrogen, creating an unequal sharing of electrons, resulting in a partial negative charge on oxygen and a partial positive charge on hydrogen. This polarity makes water a universal solvent and gives rise to properties like surface tension and hydrogen bonding. Choices A, B, and C (O, F, Br) do not form polar covalent bonds as they do not have significantly different electronegativities compared to the other element in the bond.

Correct Answer: A

Rationale: The correct answer is A because the rate of effusion of a gas is inversely proportional to the square root of its molar mass, assuming the same conditions. Since Gas A has twice the mass of Gas B, Gas B will effuse faster. Therefore, you will smell Gas A before you smell Gas B. Choice B is incorrect because Gas B will be smelled first due to its faster effusion rate. Choices C and D are incorrect because both gases will eventually be smelled due to their odorous nature, but the order of detection is based on effusion rates, not presence or absence of smell.