HESI A2
Chemistry HESI A2 Practice Test
1. When an acid is added to a base, water and a salt form. What kinds of bonds form in these two compounds?
- A. Liquid and metallic
- B. Polar and nonpolar covalent
- C. Polar covalent and ionic
- D. Ionic only
Correct answer: C
Rationale: In water, the bond formed between the oxygen atom and the hydrogen atoms is a polar covalent bond. The oxygen atom attracts the shared electrons more strongly, creating a partial negative charge on the oxygen and a partial positive charge on the hydrogen atoms. In the salt formed, the bond between the metal cation and the nonmetal anion is predominantly an ionic bond. The metal cation donates electrons to the nonmetal anion, resulting in the formation of oppositely charged ions that are held together by electrostatic attractions. Choices A and B are incorrect because water and salts do not form bonds that are liquid and metallic, or polar and nonpolar covalent. Choice D is incorrect as it oversimplifies the types of bonds present in water and salts, failing to differentiate between the covalent bond in water and the ionic bond in the salt.
2. Which element has an atomic mass greater than that of sodium?
- A. Boron
- B. Oxygen
- C. Fluorine
- D. Silicon
Correct answer: D
Rationale: Silicon has an atomic mass greater than that of sodium. The atomic mass of silicon is approximately 28.0855 u, whereas the atomic mass of sodium is approximately 22.9898 u. Therefore, silicon has a greater atomic mass compared to sodium. Boron, Oxygen, and Fluorine have atomic masses lower than sodium, making them incorrect choices in this context.
3. What is the net charge of an ionic compound?
- A. 0
- B. -1
- C. +1
- D. Variable
Correct answer: A
Rationale: The correct answer is A: 0. Ionic compounds have a net charge of 0 because they are formed by the combination of positively charged ions (cations) and negatively charged ions (anions) in a way that neutralizes their charges. This balanced combination results in an electrically neutral compound. Therefore, the net charge of an ionic compound is typically 0. Choices B, C, and D are incorrect because ionic compounds are designed to have a total neutral charge, with the positive charges balancing out the negative charges.
4. In which state of matter are particles packed tightly together in a fixed position?
- A. Liquid
- B. Solid
- C. Gas
- D. Plasma
Correct answer: B
Rationale: In a 'solid' state, particles are tightly packed in fixed positions, maintaining a definite shape and volume. This arrangement allows solids to maintain a rigid structure. Liquids have particles that are close together but can move past each other, giving them the ability to flow and take the shape of their container. Gases have particles that are far apart and move freely, leading to their ability to expand to fill any container. Plasma is an ionized gas where particles have high energy levels and are not packed tightly together, making it an uncommon state of matter on Earth.
5. What charge do Group VA elements typically have?
- A. -1
- B. -2
- C. -3
- D. 0
Correct answer: C
Rationale: Group VA elements, also known as Group 15 elements, typically have a charge of -3. This is because they have five valence electrons and tend to gain three electrons to achieve a stable octet configuration, resulting in a -3 charge. Choice A (-1) and Choice B (-2) are incorrect because Group VA elements need to gain three electrons to reach a stable electron configuration, not just one or two. Choice D (0) is also incorrect because Group VA elements do not lose electrons to form a charge of 0.
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