AP® Chemistry: Bonding, Hybridization, Intermolecular Forces, Enthalpy

Which of the following conditions is necessary for a molecule to form hydrogen bonds?

• The molecule must be nonpolar.

• Hydrogen atoms must be bonded to carbon atoms.

• Hydrogen atoms must be bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine.

• The molecule must have a high molecular mass.

What is the primary reason methanol has a higher boiling point than formaldehyde?

• Methanol has a larger molecular mass.

• Methanol can form hydrogen bonds, while formaldehyde cannot.

• Formaldehyde is nonpolar, while methanol is polar.

• Methanol has stronger London Dispersion Forces.

Why is the argument that methane molecules experience no intermolecular forces incorrect?

• Methane is a polar molecule and experiences dipole-dipole interactions.

• Methane molecules can form hydrogen bonds with each other.

• All molecules, including nonpolar ones like methane, experience London Dispersion Forces due to temporary dipoles.

• Methane has a high molecular mass, leading to strong intermolecular forces.

What formula is used to calculate the standard enthalpy change (ΔH°) for a reaction given the standard enthalpies of formation (ΔH°f) of reactants and products?

• ΔH° = ΣΔH°f(reactants) - ΣΔH°f(products)

• ΔH° = ΣΔH°f(products) - ΣΔH°f(reactants)

• ΔH° = ΔH°f(products) + ΔH°f(reactants)

• ΔH° = ΔH°f(products) / ΔH°f(reactants)

What is the standard enthalpy change (ΔH°) for the combustion of methanol, given the standard enthalpies of formation (ΔH°f) for CH₃OH(g) = -201.0 kJ/mol, O₂(g) = 0.0 kJ/mol, CO₂(g) = -393.5 kJ/mol, and H₂O(l) = -285.8 kJ/mol, and the balanced equation 2CH₃OH(g) + 3O₂(g) → 2CO₂(g) + 4H₂O(l)?

• -1528.2 kJ

• 1528.2 kJ

• -2332.2 kJ

• -1126.2 kJ

A 150.0 mL sample of methanol is used in a combustion reaction. If the density of methanol is 0.792 g/mL, what is the mass of the methanol sample?

• 119 g

• 0.00528 g

• 189.9 g

• 150.0 g

If 119 g of methanol (CH₃OH) is combusted, and its molar mass is 32.04 g/mol, how many moles of methanol are reacting?

• 3.71 moles

• 3810 moles

• 0.269 moles

• 119 moles

For the reaction 2CH₃OH(g) + 3O₂(g) → 2CO₂(g) + 4H₂O(l), the standard enthalpy change (ΔH°) is -1528.2 kJ. How much heat is released when 3.71 moles of methanol are completely combusted?

• -2830 kJ

• 2830 kJ

• -5660 kJ

• -764.1 kJ