how many neutrons does carbon 14 have

HESI A2

Chemistry HESI A2 Practice Test

1. How many neutrons does carbon-14 have?

A. 10
B. 8
C. 6
D. 12

Correct answer: B

Rationale: The correct answer is B: 8. Carbon-14 is an isotope of carbon with 6 protons and 8 neutrons. To determine the number of neutrons in an atom, subtract the atomic number (number of protons) from the mass number. In this case, the mass number of carbon-14 is 14, and the atomic number of carbon is 6. Therefore, 14 (mass number) - 6 (atomic number) = 8 neutrons. Choices A, C, and D are incorrect because they do not reflect the correct number of neutrons in a carbon-14 atom.

2. How much concentrated HCl should be used to prepare 500 mL of a 0.100 M HCl solution?

A. 75 mL
B. 100 mL
C. 125 mL
D. 150 mL

Correct answer: B

Rationale: To prepare a 0.100 M HCl solution with a volume of 500 mL, you can use the formula C1V1 = C2V2, where C1 is the concentration of the concentrated HCl solution, V1 is the volume of concentrated HCl solution used, C2 is the desired concentration (0.100 M), and V2 is the final volume (500 mL). Rearranging the formula to solve for V1, you get V1 = (C2V2) / C1. Plugging in the values (0.100 M)(500 mL) / C1 = 100 mL, which means 100 mL of concentrated HCl should be used to prepare 500 mL of a 0.100 M HCl solution. Therefore, the correct answer is 100 mL. Choice A (75 mL), Choice C (125 mL), and Choice D (150 mL) are incorrect as they do not match the calculated volume needed to prepare the desired concentration of HCl solution.

3. 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.

4. Which number represents the number of protons in an element?

A. Atomic mass
B. Mass number
C. Atomic number
D. Proton number

Correct answer: C

Rationale: The correct answer is C: Atomic number. The atomic number corresponds to the number of protons in an element. Protons are positively charged subatomic particles found in the nucleus of an atom. Each element has a unique atomic number, which defines its identity based on the number of protons it contains. Choice A, Atomic mass, is incorrect as it refers to the average mass of an atom of an element. Choice B, Mass number, represents the total number of protons and neutrons in an atom's nucleus. Choice D, Proton number, is not a commonly used term in chemistry to indicate the number of protons.

5. What is the process of breaking bonds and forming new bonds to create new chemical compounds?

A. Physical reaction
B. Chemical reaction
C. Nuclear reaction
D. Mechanical reaction

Correct answer: B

Rationale: A chemical reaction involves the breaking and forming of bonds to create new substances. During a chemical reaction, the original chemical bonds are broken, and new bonds are formed to produce one or more new substances with different properties from the reactants. This transformation is a fundamental concept in chemistry and distinguishes chemical reactions from physical, nuclear, or mechanical reactions. Choice A, 'Physical reaction,' does not involve the breaking and forming of chemical bonds but rather changes in physical state or appearance. Choice C, 'Nuclear reaction,' involves changes in the nuclei of atoms, not the breaking and forming of chemical bonds. Choice D, 'Mechanical reaction,' refers to reactions involving physical forces or movements, not the breaking and forming of chemical bonds as in a chemical reaction.