Chemistry Hesi A2 - Nurselytic

Correct Answer: C

Rationale: Aluminum (Al) has an atomic number of 13, which indicates it normally has 13 electrons to balance the 13 protons in its nucleus. When Al forms an Al3+ ion, it loses 3 electrons to achieve a stable electron configuration.
Therefore, the Al3+ ion will have 13 - 3 = 10 electrons.
Choice A (16) is incorrect as it doesn't take into account the charge of the Al3+ ion.
Choice B (13) is incorrect because the Al3+ ion has lost electrons.
Choice D (3) is incorrect as it doesn't reflect the total number of electrons lost by the Al atom to form the Al3+ ion.

Correct Answer: A

Rationale: A blood pH of 3 is significantly low, indicating a strong acidity level. The normal blood pH range is 7.35 to 7.45; therefore, a pH of 3 is far below the normal range, showing a highly acidic condition in the blood sample.
Choice B is incorrect because a pH of 3 is not basic at all.
Choice C is incorrect as a pH of 3 is not weakly acidic but strongly acidic.
Choice D is wrong as a blood pH of 3 does not indicate a weakly basic condition.

Correct Answer: C

Rationale: The half-life of a radioactive isotope is the time it takes for half of the original sample to decay. After each half-life period, half of the initial sample remains. In this case, after the first 20 years, half of the 6-gram sample (3 grams) will remain. After another 20 years (total of 40 years), half of the remaining 3 grams will remain, which is 1.5 grams.
Therefore, 3 grams will be left after 40 years.
Choice A is incorrect as it doesn't consider the concept of half-life and incorrectly suggests an increase in the sample.
Choice B is incorrect as it assumes no decay over time.
Choice D is incorrect as it miscalculates the remaining amount after two half-life periods.

Correct Answer: D

Rationale: The compound CHâ‚„, methane, has a nonpolar bond where carbon and hydrogen share electrons equally. This occurs because carbon and hydrogen have similar electronegativities, meaning they have equal abilities to attract shared electrons. Consequently, a nonpolar covalent bond is formed due to the balanced sharing of electrons between these atoms.

Choices A, B, and C do not have nonpolar bonds with electrons shared equally. In H₂O (water), there are polar covalent bonds due to the difference in electronegativity between hydrogen and oxygen. In NH₃ (ammonia), the nitrogen-hydrogen bonds are polar because of the electronegativity difference. In Cl₂ (chlorine gas), the Cl-Cl bond is nonpolar, but the question specifies a compound, not an element, and chlorine does not share its electrons equally with another element in a compound.

Correct Answer: C

Rationale: The reaction shown (8Fe + S → 8FeS) is a synthesis reaction. In a synthesis reaction, two or more substances combine to form a single compound. In this case, iron (Fe) and sulfur (S) combine to form iron sulfide (FeS). The key characteristic of a synthesis reaction is the formation of a single product from multiple reactants, which aligns with the given chemical equation.
Choice A, single displacement, involves an element displacing another in a compound, which is not the case here.
Choice B, double displacement, involves the exchange of ions between two compounds, which is also not happening in this reaction.
Choice D, acid-base, refers to reactions between an acid and a base to form salt and water, which is not the case in the given equation.