HESI A2
HESI A2 Version 1 Chemistry Questions
Question 1 of 5
How can water be boiled at room temperature?
Correct Answer: B
Rationale: Water boils when its vapor pressure equals the atmospheric pressure. By increasing the pressure, the atmospheric pressure is reached at a lower temperature, allowing water to boil at room temperature. This phenomenon is utilized in specific scenarios such as high-altitude cooking where the reduced atmospheric pressure requires an increase in the boiling point to cook food properly. Therefore, the correct answer is by increasing the pressure.
Question 2 of 5
What is the term for the reactant that is entirely consumed by the reaction?
Correct Answer: A
Rationale: The correct answer is A, limiting reactant. In a chemical reaction, the limiting reactant is the substance that is entirely consumed when the reaction reaches completion. It determines the maximum amount of product that can be formed. The reducing agent (choice B) is a substance that donates electrons to another chemical species, the reaction intermediate (choice C) is a molecule formed and consumed in different steps of the reaction, and a reagent (choice D) is a general term for any substance participating in a chemical reaction.
Question 3 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.
Question 4 of 5
What does the term 'atomic number' represent?
Correct Answer: B
Rationale: The atomic number represents the number of protons in the nucleus of an atom. This number uniquely identifies an element and determines its placement in the periodic table. The number of neutrons and electrons can vary among different isotopes of an element, but the number of protons remains constant, defining the element's atomic number. Therefore, the correct answer is the number of protons (Choice B).
Question 5 of 5
What is the charge on potassium in the compound KCl?
Correct Answer: B
Rationale: In the compound KCl, the overall charge must be zero since it is a neutral compound. Chlorine (Cl) typically has a charge of -1 in ionic compounds. Therefore, for the compound to be neutral, potassium (K) must have a charge of +1 to balance the -1 charge of chlorine. This results in a total charge of 0 for the compound. Thus, the correct answer is +1. The positively charged potassium ion (K+) combines with the negatively charged chloride ion (Cl-) to form an electrically neutral compound, potassium chloride (KCl).