HESI A2 Version 1 Chemistry

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.

Correct Answer: C

Rationale: A redox reaction, short for reduction-oxidation reaction, involves the transfer of electrons from one reactant to another. In these reactions, one substance is oxidized (loses electrons) while another is reduced (gains electrons). The term 'redox' comes from the simultaneous occurrence of reduction and oxidation reactions. Combustion reaction (choice A) involves a substance reacting with oxygen to produce heat and light, but it does not necessarily involve electron transfer. Synthesis reaction (choice B) involves the combination of two or more substances to form a new compound, with no mention of electron transfer. Double-displacement reaction (choice D) involves an exchange of ions between two compounds but does not specifically involve electron transfer between atoms. Therefore, option C, redox reaction, is the correct answer as it accurately describes the electron transfer process that occurs during such reactions.

Correct Answer: A

Rationale: The periodic table is a fundamental tool in chemistry that organizes elements based on their properties. By using the periodic table, scientists can predict the properties of each element. The arrangement of elements in the table groups together elements with similar characteristics, allowing for the prediction of various properties such as reactivity, atomic size, and electronegativity. These predictions are possible because elements in the same group or period exhibit similar chemical behaviors. Therefore, the correct answer is A: The properties of each of the elements.

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).