HESI A2 Chemistry Practice Test

Correct Answer: B

Rationale: The correct answer is B: Hydrogen bonds. Hydrogen bonds are formed between a hydrogen atom in a polar covalent bond and a highly electronegative atom like oxygen or nitrogen. In water, hydrogen bonds contribute to its high boiling point, surface tension, and density anomalies. In DNA, hydrogen bonds between base pairs help maintain the double helix structure. Incorrect choices: A: Oxygen links - This is not a recognized term in chemistry and does not accurately describe the type of bonds discussed. C: Dipolar bonds - While dipole-dipole interactions are involved in hydrogen bonding, the term "dipolar bonds" is not commonly used to refer to this specific type of bond. D: N/A - This choice does not provide any information related to the question and is not a valid option.

Correct Answer: A

Rationale: The correct answer is A: Covalent bonds. Covalent bonds involve a complete sharing of electrons between atoms with partially filled outer shells. This sharing allows atoms to achieve stable electron configurations. Hydrogen bonds involve an electrostatic attraction between a hydrogen atom and a highly electronegative atom. Proportional bonds are not a recognized type of chemical bond. Choice D, N/A, is not a valid option for this question.

Correct Answer: B

Rationale: The correct answer is B: Alloys. Alloys are mixtures of 2 or more metals, where the metals are evenly distributed at a microscopic level. This creates unique properties different from the individual metals. Solutions (A) involve a solute dissolved in a solvent, not necessarily metals. Compounds (C) are formed by chemical bonding between elements, not just a mixture. Suspensions (D) are mixtures where particles are suspended in a fluid but eventually settle out, unlike alloys which are uniform mixtures.

Correct Answer: B

Rationale: The correct answer is B: 20. Essential amino acids are those that the human body cannot produce on its own and must be obtained from diet. Humans require 9 essential amino acids. Since the total number of amino acids required for human life is 20, including the 9 essential ones, the correct answer is 20. Choices A, C, and D are incorrect because they do not align with the established fact that humans need 20 amino acids for survival, with 9 being essential.

Correct Answer: A

Rationale: The correct answer is A: Order of increasing atomic number. This is because the periodic table is arranged based on the number of protons in the nucleus of an atom, which is the atomic number. This arrangement helps in organizing elements based on their properties and allows us to predict the behavior of elements. Choice B (Alphabetical order) is incorrect because elements are not arranged alphabetically but based on their atomic number. Choice C (Order of increasing metallic properties) is incorrect because while elements are grouped based on similar properties, the overall arrangement is not solely based on metallic properties. Choice D (Order of increasing neutron content) is incorrect as the periodic table is based on atomic number (number of protons), not neutron content.