HESI A2
Chemistry HESI A2 Quizlet
1. What charge do Group IA elements have?
- A. +1
- B. +2
- C. +3
- D. 0
Correct answer: A
Rationale: Group IA elements, also known as alkali metals, have a +1 charge. They readily lose one electron to achieve a stable electron configuration, forming ions with a single positive charge. This makes +1 the correct choice. Choices B, C, and D are incorrect because alkali metals in Group IA typically lose one electron, so they do not have a +2, +3, or 0 charge.
2. What is matter that has a definite shape and volume?
- A. Liquid
- B. Solid
- C. Gas
- D. Plasma
Correct answer: B
Rationale: Matter that has a definite shape and volume is referred to as a solid. Solids maintain their shape and volume under normal conditions, unlike liquids that have a definite volume but take the shape of their container, gases that have neither a definite shape nor volume, and plasma which is a state of matter with no definite shape or volume and consists of charged particles.
3. What are the horizontal rows of the periodic table called?
- A. Periods
- B. Families
- C. Groups
- D. Columns
Correct answer: A
Rationale: The correct answer is A: Periods. Rows in the periodic table are called periods. They are arranged horizontally from left to right and represent the energy levels of the elements. Each period starts a new energy level or shell, indicating the number of electron shells an element has. Choices B, C, and D are incorrect. Families and groups refer to vertical columns in the periodic table that share similar chemical properties, while columns are vertical arrangements of elements known as groups or families.
4. To the nearest whole number, what is the mass of one mole of sodium chloride?
- A. 36 g/mol
- B. 43 g/mol
- C. 58 g/mol
- D. 72 g/mol
Correct answer: C
Rationale: The molar mass of sodium chloride (NaCl) is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl). The atomic mass of sodium is approximately 23 g/mol and chlorine is approximately 35.5 g/mol. Adding these two atomic masses gives us a molar mass of approximately 58 g/mol for sodium chloride (NaCl). Therefore, the correct answer is C, 58 g/mol. Choice A (36 g/mol) is incorrect as it does not account for the individual atomic masses of sodium and chlorine. Choice B (43 g/mol) and choice D (72 g/mol) are also incorrect as they do not reflect the accurate molar mass of sodium chloride.
5. What is the molarity of a solution containing 45 moles of NaCl in 4 liters?
- A. 0.11 M NaCl
- B. 0.45 M NaCl
- C. 1.8 M NaCl
- D. 8.9 M NaCl
Correct answer: A
Rationale: To calculate the molarity of a solution, you use the formula: Molarity (M) = moles of solute / liters of solution. In this case, M = 45 moles / 4 L = 11.25 M. The correct answer is 0.11 M NaCl. Choice B is incorrect as it doesn't match the calculated value. Choice C is also incorrect as it is significantly higher than the correct molarity. Choice D is incorrect as it is excessively high compared to the calculated value.
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