FREE AP Chemistry Exam Trivia Question and Answers

Question 1

When 1 mole of potassium dichromate and 3 moles of nickel are combined, how many moles of electrons are transferred?

Accepted Answer

six moles of electrons

Answer

In the reaction between potassium dichromate (K₂Cr₂O₇) and nickel (Ni), chromium in dichromate is reduced from an oxidation state of +6 to +3. Since there are two chromium atoms in Cr₂O₇²⁻, the reduction of one dichromate ion involves a gain of 2 * (6-3) = 6 electrons. Nickel is oxidized from 0 to Ni²⁺, losing 2 electrons per atom. To balance the 6 electrons gained by dichromate, 3 moles of nickel are needed (3 moles Ni * 2 electrons/mole Ni = 6 electrons lost). Thus, a total of six moles of electrons are transferred.

Question 2

Which of the following circumstances results in the bond length between any two nonmetal atoms?

Accepted Answer

Where the energy of interaction between the atoms is at its minimum value

Answer

The bond length between two nonmetal atoms is the average distance between their nuclei when the potential energy of the system is at its minimum. At this specific distance, the attractive forces between the nuclei and electrons are optimally balanced with the repulsive forces between the nuclei and between the electrons, resulting in the most stable and lowest energy configuration for the chemical bond.

Question 3

At 15°C, hydrogen fluoride, or HF, is a liquid. At the same temperature, all other hydrogen halides (represented by HX, where X is any other halogen) are gases. Why?

Accepted Answer

The dipoles in an HF molecule exhibit a particularly strong attraction force to the dipoles in other HF molecules.

Answer

Hydrogen fluoride (HF) exhibits strong hydrogen bonding, which is an exceptionally strong type of intermolecular force. This occurs because fluorine is highly electronegative and bonded to hydrogen, creating a very polar H-F bond. These strong attractions between HF molecules require significantly more energy to overcome for the molecules to enter the gas phase, explaining HF's unusually high boiling point and its liquid state at 15°C compared to other hydrogen halides.

Question 4

The subatomic particle with the greatest power to penetrate is

Accepted Answer

a beta particle

Answer

Beta particles are high-energy electrons or positrons that are significantly lighter and faster than alpha particles. Their smaller mass and single unit of charge result in less intense interactions with the electrons of the absorbing material compared to the heavier, doubly charged alpha particles or protons. This allows beta particles to travel further and penetrate deeper into substances, making them the most penetrating among the given charged options.

Question 5

Which of the following bonds has its negative end written last?

Accepted Answer

P—CI

Answer

The negative end of a polar covalent bond is located on the atom with the higher electronegativity, as it attracts the shared electrons more strongly. In the P—Cl bond, chlorine (electronegativity ≈ 3.16) is significantly more electronegative than phosphorus (electronegativity ≈ 2.19). Therefore, the electron density is pulled more towards the chlorine atom, making it the negative end of the dipole, which is written last in the P—Cl notation.

AP Practice Test

AP Practice Test

FREE AP Chemistry Exam Trivia Question and Answers