The molar mass of some gases is as follows: carbon monoxide-28.01 g/mol; helium-4.00 g/mol; nitrogen-28.01 g/mol; and oxygen-32.00 g/mol. Which would you expect to diffuse most rapidly?

Correct Answer: B

Rationale: The rate of diffusion is inversely proportional to the molar mass of the gas. Helium has the lowest molar mass among the given gases, making it the lightest and fastest gas to diffuse. Therefore, helium would be expected to diffuse most rapidly compared to carbon monoxide, nitrogen, and oxygen. Carbon monoxide, nitrogen, and oxygen have higher molar masses than helium, so they would diffuse more slowly. Therefore, the correct answer is helium.

Correct Answer: B

Rationale: The rate of diffusion is inversely proportional to the molar mass of the gas. Helium has the lowest molar mass among the given gases, making it the lightest and fastest gas to diffuse. Therefore, helium would be expected to diffuse most rapidly compared to carbon monoxide, nitrogen, and oxygen. Carbon monoxide, nitrogen, and oxygen have higher molar masses than helium, so they would diffuse more slowly. Therefore, the correct answer is helium.

Correct Answer: B

Rationale: Noble gases are non-polar molecules without a permanent dipole moment. The only intermolecular force applicable to noble gases is the London dispersion force, also known as Van der Waals forces. This force is a temporary attractive force resulting from the formation of temporary dipoles in non-polar molecules. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding involve significant dipoles or hydrogen atoms bonded to electronegative atoms, which do not apply to noble gases.

Correct Answer: C

Rationale: The molar mass of hydrogen chloride (HCl) is calculated by adding the atomic masses of hydrogen (H) and chlorine (Cl) together. The atomic mass of hydrogen is approximately 1 g/mol, and the atomic mass of chlorine is approximately 35.5 g/mol. Therefore, the molar mass of hydrogen chloride (HCl) is approximately 1 + 35.5 = 36.5 g/mol. When rounded to the nearest whole number, it is 36 g/mol. Therefore, the correct answer is 36 g/mol. Choices A, B, and D are incorrect as they do not reflect the accurate molar mass of hydrogen chloride.

Correct Answer: C

Rationale: The given unbalanced equation is Zn + HCl → ZnCl + H2. To balance it, we need to have equal atoms on both sides of the equation. The balanced equation is 2Zn + 2HCl → 2ZnCl + H2. This balanced equation shows that two atoms of Zn combine with two molecules of HCl to form two molecules of ZnCl and one molecule of H2. Choice A is incorrect because it does not balance the equation. Choice B is incorrect as it does not have the same number of atoms on both sides. Choice D is incorrect because it does not balance the equation properly, resulting in an unequal number of atoms on both sides.

Correct Answer: C

Rationale: The reaction shown (8Fe + S → 8FeS) is a synthesis reaction. In a synthesis reaction, two or more substances combine to form a single compound. In this case, iron (Fe) and sulfur (S) combine to form iron sulfide (FeS). The key characteristic of a synthesis reaction is the formation of a single product from multiple reactants, which aligns with the given chemical equation. Choice A, single displacement, involves an element displacing another in a compound, which is not the case here. Choice B, double displacement, involves the exchange of ions between two compounds, which is also not happening in this reaction. Choice D, acid-base, refers to reactions between an acid and a base to form salt and water, which is not the case in the given equation.

Correct Answer: C

Rationale: Potassium iodide (KI) shows a decrease in solubility in water with an increase in temperature. This is due to the dissolution of KI in water being an endothermic process. When the temperature rises, the equilibrium shifts toward the solid state, leading to a decrease in solubility. Therefore, as the temperature increases, KI becomes less soluble in water. Choice A (NaCl) and Choice D (CaCl) do not exhibit a decrease in solubility with an increase in temperature. NaCl and CaCl are generally more soluble in water at higher temperatures. Choice B (Oxygen) is a gas and not typically considered in solubility discussions involving solids or liquids dissolving in water.

Correct Answer: A

Rationale: Ozone (O3) is a triatomic allotrope of oxygen. It differs from the common diatomic oxygen molecule (O2) by having three oxygen atoms bonded together. Ozone is known for its protective role in the Earth's atmosphere, absorbing most of the Sun's harmful ultraviolet radiation. Water (H2O) is a compound composed of two hydrogen atoms and one oxygen atom. Acidic oxide and carbon dioxide are not triatomic allotropes of oxygen. Carbon dioxide consists of one carbon atom and two oxygen atoms, while acidic oxides refer to compounds where oxygen is bonded with other elements to form oxides, and they are not allotropes of oxygen.

Correct Answer: A

Rationale: In the solid state, you would expect a nonmetal to be brittle. Nonmetals generally lack the malleability and ductility of metals, which makes them prone to being brittle and easily fractured under stress. This property is due to the lack of metallic bonding in nonmetals, which results in a more rigid and less flexible structure. Choice B, 'lustrous,' is incorrect because nonmetals typically do not exhibit a shiny or reflective surface like metals do. Choice C, 'malleable,' is also incorrect as nonmetals lack the ability to be hammered or rolled into thin sheets like metals. Choice D, 'conductive,' is incorrect since nonmetals are generally poor conductors of electricity compared to metals.