ACS Practice Quiz for Exam Success

The proton is the subatomic particle with a positive charge and is located in the nucleus. Electrons carry a negative charge while neutrons have no charge.

The chemical symbol for sodium is Na, which is derived from its Latin name 'Natrium.' The other options do not correctly represent sodium's symbol.

Hydrogen has the lowest atomic number of 1, making it the first element on the periodic table. The other elements have higher atomic numbers.

Solids have a fixed shape and volume because their particles are closely packed together. In contrast, liquids and gases adapt their shapes to the containers they occupy.

Burning paper is a chemical change because it involves a reaction that produces new substances, such as ash and gases. The other processes are physical changes where the original substance remains chemically unchanged.

Electronegativity measures how strongly an atom attracts electrons in a chemical bond. A higher electronegativity indicates a stronger pull on the bonding electrons.

Atomic radius decreases across a period because the increasing nuclear charge pulls electrons closer to the nucleus. This trend is consistently observed in the periodic table.

Ionic bonds form when one atom transfers electrons to another, creating oppositely charged ions that attract each other. This contrasts with covalent bonds, where electrons are shared between atoms.

The mole is a fundamental counting unit in chemistry that equates to 6.02 x 10^23 particles of a substance. This concept links the macroscopic amounts of material with the number of atoms or molecules present.

The balanced combustion equation for methane requires one mole of CH4 reacting with two moles of O2 to produce one mole of CO2 and two moles of H2O. This ensures that the number of atoms for each element is conserved in the reaction.

The balanced equation indicates that 2 moles of hydrogen and 1 mole of oxygen yield 2 moles of water. This is a direct application of stoichiometry where the mole ratio is maintained.

Oxidation involves the loss of electrons from a chemical species. This process is typically paired with reduction, where another species gains the electrons lost.

An acidic solution has a pH value below 7, indicating a higher concentration of hydrogen ions. A pH of 7 is neutral, while values above 7 denote basic solutions.

Double displacement reactions occur when the ions of two compounds swap partners, often leading to a precipitate, gas, or water formation. This reaction type is common in aqueous solutions and follows a predictable pattern.

A catalyst speeds up a chemical reaction by providing an alternative pathway with a lower activation energy. It is not consumed in the reaction and does not affect the overall energy change of the reaction.

By reversing the second reaction and adding it to the first, the enthalpy change for the formation of CO is calculated as -393 kJ/mol + 283 kJ/mol, which equals -110 kJ/mol. This use of Hess's law demonstrates that enthalpy is a state function.

A very large equilibrium constant indicates that the concentration of products at equilibrium is significantly higher than that of the reactants. This means the reaction strongly favors the formation of products.

Methane has four bonding pairs and no lone pairs around the central carbon atom, which results in a tetrahedral molecular geometry. This arrangement minimizes electron pair repulsion as described by VSEPR theory.

Increasing the temperature raises the kinetic energy of the reacting molecules, leading to more frequent and energetic collisions. This generally results in an increased reaction rate as described by the Arrhenius equation.