HESI A2 Chemistry

Correct Answer: C

Rationale: To determine the time for the substance to decay to 7 kg, we need to calculate the number of half-lives required. Each half-life reduces the substance by half. Given: Initial mass = 56 kg, Final mass = 7 kg, Half-life = 12 days. Number of half-lives = log(final mass / initial mass) / log(0.5) = log(7/56) / log(0.5) = 3.807 / -0.301 = -12.66. As the number of half-lives must be a whole number, we round up to 13 half-lives. Total time = 13 * 12 days = 156 days. Therefore, the correct answer is C (36 days). The other choices are incorrect because they do not accurately represent the calculation based on the half-life of the substance.

Correct Answer: D

Rationale: The correct answer is D: W (tungsten). Tungsten has the greatest atomic mass among the elements listed. Tungsten has an atomic number of 74, which corresponds to an atomic mass of approximately 183.84 g/mol. Gold (Au) has an atomic number of 79, with an atomic mass of around 196.97 g/mol, making it heavier than barium (Ba) and iodine (I). Barium has an atomic number of 56, with an atomic mass of about 137.33 g/mol, and iodine has an atomic number of 53, with an atomic mass of roughly 126.90 g/mol. Therefore, tungsten (W) has the greatest atomic mass compared to the other elements listed.

Correct Answer: B

Rationale: The correct answer is B: Amino acids. Proteins are made up of long chains of amino acids, which are the building blocks of proteins. Amino acids are linked together by peptide bonds to form polypeptide chains, which then fold into complex 3D structures to create proteins. Fatty acids (choice A) are lipids, nucleotides (choice C) are the building blocks of nucleic acids like DNA and RNA, and sugars (choice D) are carbohydrates. Therefore, choices A, C, and D are incorrect as they do not make up proteins.

Correct Answer: D

Rationale: The correct answer is D: ionization energy. Ionization energy is the energy needed to remove an electron from an atom. The outermost electron requires the least amount of energy to remove as it is farthest from the nucleus. This process results in the formation of a positively charged ion. Explanation: 1. Covalent bonding (A) refers to the sharing of electrons between atoms, not the energy required to remove an electron. 2. Electronegativity (B) is the ability of an atom to attract electrons in a chemical bond, not the energy needed to remove an electron. 3. Atomic radius (C) is the size of an atom, which does not directly relate to the energy required to remove an electron.

Correct Answer: C

Rationale: Failed to generate a rationale after 5 retries.