HESI A2 Chemistry Questions with Answers and Explanations (A Graded) Latest Questions and Complete Solutions

HESI A2 Chemistry Questions with Answers and Explanations (A Graded) Latest Questions and Complete Solutions 1. Which of the following elements is not involved in many hydrogen bonds? A. fluorine B. carbon C. oxygen D. nitrogen Explanation: Carbon is not involved in many hydrogen bonds. A hydrogen bond occurs when an atom of hydrogen that has a covalent bond with an electronegative atom forms a bond with a third atom. The original covalent bond involving hydrogen gives away protons, and the third element receives them. One of the reasons that fluorine, oxygen, and nitrogen are frequently part of a hydrogen bond is that they have a strong electronegativity and are therefore able to form more durable bonds. Chlorine is another element frequently involved in hydrogen bonds. 2. What is the mass (in grams) of 0.350 mol copper? A. 12.5 g B. 14.6 g C. 18.5 g D. 22.2 g Explanation: The mass of 0.350 mol copper is 22.2 grams. This problem requires the use of the periodic table. There you will see that the molecular mass of copper is approximately 63.5. Take this figure and multiply it by the amount of copper given by the question: 0.350 mol. The resulting figure is 22.225, which, rounded to the nearest tenth, is 22.2 grams. In order to succeed on the HESI exam, you will need to be able to perform these simple calculations of mass. 3. How many d orbitals are there in a d subshell? A. 5 B. 7 C. 9 D. 11 Explanation: There are five d orbitals in a d subshell (or sublevel). Each of these orbitals can hold two electrons, so sublevel d is capable of holding 10 electrons. The s subshell has one orbital, the p subshell has three orbitals, the d subshell has five orbitals, and the f subshell has seven orbitals. In chemistry, the electron configuration of an atom is expressed in the following form, using helium as an example: 1s2. In this notation, the 1 indicates that the electrons are found in the first energy level of the atom, the s indicates that the electrons are in a spherical orbit, and the superscript 2 indicates that there are 2 total electrons in the first energy level subshell. 4. What is the name for the number of protons in an atom? a. atomic identity b. atomic mass c. atomic weight d. atomic number Explanation: The number of protons in an atom is the atomic number. Protons are the fundamental positive unit of an atom. They are located in the nucleus. In a neutral atom (an atom with neither positive nor negative charge), the number of protons in the nucleus is equal to the number of electrons orbiting the nucleus. When it needs to be expressed, atomic number is written as a subscript in front of the element’s symbol, for example in 13Al. Atomic mass, meanwhile, is the average mass of the various isotopes of a given element. Atomic identity and atomic weight are not concepts in chemistry. 5. Which of the following elements is an alkali metal? a. magnesium b. rubidium c. hydrogen d. chlorine Explanation: Rubidium is an alkali metal. The alkali metals are located in group 1 of the periodic table. These soft substances melt at a low temperature and are typically white in color. The alkali metals are lithium, sodium, potassium, rubidium, cesium, and francium. Rubidium, cesium, and francium are not commonly encountered in the natural world. The alkali metals are highly reactive, meaning that they easily engage in chemical reactions when combined with other elements. These metals have a low density and tend to react violently with water