HESI A2
HESI A2 Version 1 Chemistry Questions
Question 1 of 5
What are van der Waals forces?
Correct Answer: A
Rationale: Van der Waals forces are weak intermolecular forces that occur between non-polar molecules. These forces result from temporary fluctuations in electron distribution within the molecules, leading to slight positive and negative charges. This results in weak attraction between molecules through van der Waals forces. Hydrogen bonds, in contrast, are stronger intermolecular forces that specifically occur between molecules containing hydrogen bonded to a highly electronegative atom like oxygen or nitrogen. Conjugal bonds do not exist in chemistry and are not relevant to intermolecular forces.
Question 2 of 5
Chemical reactions in living systems proceed along catabolic pathways, and there tends to be an increase in which of the following?
Correct Answer: A
Rationale: In catabolic pathways, complex molecules are broken down into simpler ones, leading to an increase in disorder or entropy. Entropy represents the measure of randomness or disorder in a system. As chemical reactions break down molecules, the overall disorder in the system tends to increase, making entropy the correct answer in this context. Therefore, the correct answer is 'Entropy' as it aligns with the concept of increased disorder in catabolic pathways. Enthalpy, on the other hand, relates to the total heat content of a system and is not specifically associated with disorder or complexity. Glucose and glycogen are molecules involved in energy storage and are not directly related to the increase in disorder observed in catabolic pathways.
Question 3 of 5
What is the name for the horizontal rows of the periodic table?
Correct Answer: B
Rationale: In the periodic table, the horizontal rows are called 'periods.' These periods represent the number of electron shells an element has. Each period starts a new energy level, indicating the elements' properties and atomic structure. 'Groups' refer to the vertical columns of the periodic table, each containing elements with similar chemical properties. 'Families' can also be used interchangeably with groups. 'Sets' is a vague term and not specifically related to the layout of the periodic table. Understanding the distinction between 'periods' and 'groups' is crucial in comprehending the organization and properties of elements in the periodic table.
Question 4 of 5
Which of the following elements is an alkali metal?
Correct Answer: B
Rationale: Rubidium is the correct answer because alkali metals are found in Group 1 of the periodic table. Rubidium is located in Group 1 and exhibits properties typical of alkali metals, such as low melting points, high reactivity, and the tendency to form ionic compounds. Magnesium is an alkaline earth metal, hydrogen is a nonmetal, and chlorine is a halogen, so they do not belong to the alkali metal group.
Question 5 of 5
What is a combustion reaction?
Correct Answer: D
Rationale: A combustion reaction is a type of chemical reaction that involves a substance reacting with oxygen gas to produce heat and light. This reaction is exothermic, releasing energy in the form of heat and light. The correct answer is D because combustion reactions specifically involve oxygen as a reactant, leading to the production of heat and light as byproducts.