Protons have a positive charge and are found in the nucleus of an atom. Electrons are negatively charged and neutrons have no charge.

Water is the most common solvent due to its polarity and its ability to dissolve a wide range of substances. The other solvents are less common in typical aqueous reactions.

A catalyst accelerates a reaction by providing an alternative pathway with a lower activation energy while remaining unchanged. Other options either participate in the reaction or interfere with it.

The law of conservation of mass tells us that mass is conserved in a closed system during chemical reactions. Other laws relate to the proportions of elements or energy conservation.

Noble gases occupy Group 18 in the periodic table and are characterized by their chemical inertness. The other groups refer to alkali metals, alkaline earth metals, and chalcogens respectively.

According to VSEPR theory, a molecule with four bonding pairs and no lone pairs around the central atom adopts a tetrahedral geometry. The other geometries require different electron domain counts or lone pair arrangements.

Vaporization is the process by which a liquid absorbs energy to become a gas. Condensation is the opposite process; sublimation refers to a solid turning directly into a gas, and fusion is melting.

Reduction is defined as the gain of electrons during a chemical reaction, while oxidation is the loss of electrons. Only one species undergoes reduction in any given redox reaction.

The pH scale quantitatively measures the concentration of hydrogen ions (H+) in a solution. Lower pH values correspond to higher H+ concentrations, indicating acidity.

Kc is defined in terms of the molar concentrations of the species at equilibrium, while Kp is defined using the partial pressures of gaseous species. Ka and Kb are used for acid and base dissociation constants.

A balanced chemical equation conveys the precise mole ratios required for reactants to convert to products, which is crucial for calculating theoretical yields. It does not provide information on rate or energy changes.

Molarity is a concentration unit defined as the number of moles of solute divided by the volume of the solution in liters. The other options mix up units or refer to different measurements.

Collision theory requires that for a reaction to occur, molecules must collide with sufficient energy and proper orientation. Frequent collisions without proper conditions do not guarantee a reaction.

Catalysts work by offering an alternative reaction pathway that requires less energy for the reaction to proceed. They do not alter the temperature, concentration, or equilibrium position of the system.

Ionic bonds form when electrons are transferred from one atom to another, creating ions, whereas covalent bonds form when atoms share electrons. The other statements are misconceptions about bond nature.

The number of moles is calculated by dividing the mass by the molar mass: 25.0 g / 18 g/mol ≈ 1.39 moles. This is the correct computation using dimensional analysis.

According to the stoichiometric ratio, 2 moles of A require 3 moles of B. For 4 moles of A, 6 moles of B are needed. Since 9 moles of B are available, A is the limiting reagent.

Endothermic reactions absorb heat from their surroundings, causing an increase in the system's enthalpy. The other options describe exothermic reactions or unrelated phenomena.

At equilibrium, the forward and reverse reaction rates balance each other, maintaining constant concentrations. It is a dynamic equilibrium where molecular activity continues despite no net change.

Le Chatelier's Principle states that increasing the concentration of a reactant will cause the system to adjust by shifting the equilibrium toward the products, reducing the disturbance. The other options do not correctly represent the principle.