what is the correct electron configuration for carbon

HESI A2

Chemistry Hesi A2

1. What is the correct electron configuration for carbon?

A. 1sÂ²2sÂ²2pÂ¹
B. 1sÂ²2sÂ²2pÂ²
C. 1sÂ²2sÂ²2pÂ³
D. 1sÂ²2sÂ²2pâ¶3sÂ¹

Correct answer: B

Rationale: The correct electron configuration for carbon is 1sÂ²2sÂ²2pÂ². This configuration indicates that there are 2 electrons in the first energy level (1sÂ²), 2 electrons in the second energy level (2sÂ²), and 2 electrons in the second energy level (2pÂ²). It adheres to the aufbau principle, which states that electrons fill orbitals starting from the lowest energy level, and the Pauli exclusion principle, which states that each electron in an atom must have a unique set of quantum numbers. Choice A is incorrect because it does not fill the 2p orbital correctly. Choice C is incorrect as it exceeds the number of possible electrons in the 2p orbital. Choice D is incorrect as it includes an electron in the 3s orbital, which is not part of the electron configuration for carbon.

2. Why does the diffusion rate increase as a substance is heated?

A. The kinetic energy of particles increases.
B. The space between particles increases.
C. The density of particles decreases.
D. The size of particles increases.

Correct answer: A

Rationale: The correct answer is A. When a substance is heated, the kinetic energy of particles increases, causing them to move faster. This increased movement allows the particles to spread out more rapidly, leading to a higher diffusion rate. Choice B is incorrect because heating does not directly affect the space between particles. Choice C is incorrect because heating does not necessarily lead to a decrease in the density of particles. Choice D is incorrect because the size of particles does not necessarily increase when a substance is heated. Therefore, the correct explanation for the increase in diffusion rate is the rise in kinetic energy of particles.

3. When balanced, the reaction Fe + Oâ‚‚ â†’ FeO will be?

A. 2Fe + 2Oâ‚‚ â†’ 3FeO
B. 4Fe + 6Oâ‚‚ â†’ 6FeO
C. 2Fe + 3Oâ‚‚ â†’ 2FeO
D. 4Fe + 3Oâ‚‚ â†’ 2FeO

Correct answer: C

Rationale: To balance the chemical equation Fe + Oâ‚‚ â†’ FeO, the coefficients needed are 2 for Fe and 1 for O. Therefore, the balanced equation becomes 2Fe + Oâ‚‚ â†’ 2FeO, which translates into 2Fe + 3Oâ‚‚ â†’ 2FeO. This corresponds to option C. Choice A has the incorrect number of oxygen molecules. Choice B has an incorrect number of Fe atoms on the product side. Choice D also has an incorrect number of Fe atoms on the product side.

4. What defines a balanced chemical equation?

A. An equation where the number of atoms of each element is the same on both sides
B. An equation where there are more products than reactants
C. An equation where the number of molecules is balanced
D. An equation with equal masses on both sides

Correct answer: A

Rationale: A balanced chemical equation is one in which the number of atoms of each element is the same on both sides. This balance ensures the law of conservation of mass is upheld, where the total mass of the reactants equals the total mass of the products. Options B, C, and D are incorrect. Option B is incorrect as a balanced equation has an equal number of products and reactants. Option C is incorrect as balancing refers to the number of atoms, not molecules. Option D is incorrect as balancing is based on the number of atoms, not masses. Therefore, option A is the correct choice as it accurately describes a balanced chemical equation.

5. Which type of chemical reaction involves an active metal reacting with an ionic compound to create a new compound?

A. Combustion
B. Single replacement
C. Synthesis
D. Decomposition

Correct answer: B

Rationale: The correct answer is 'Single replacement.' In a single replacement reaction, an active metal replaces another element in an ionic compound, resulting in the formation of a new compound. Option A, 'Combustion,' involves a substance rapidly reacting with oxygen to release energy in the form of heat and light. Option C, 'Synthesis,' involves the combination of two or more substances to form a more complex product. Option D, 'Decomposition,' involves the breakdown of a compound into simpler substances.