M5L1 - MP Quiz - Rates and Orders of Reaction

Enthalpy of formation is defined as:

• The enthalpy change when one mole of a compound is formed from its elements in their standard states.

• The enthalpy change when one mole of a compound is decomposed into its elements.

• The enthalpy change when one mole of a substance is dissolved in water.

• The enthalpy change when one mole of a substance is vaporized.

Enthalpy of combustion is defined as:

• The heat change when one mole of a substance is completely burned in oxygen.

• The heat change when one mole of a substance is dissolved in water.

• The heat change when one mole of a substance is formed from its elements.

• The heat change when one mole of a substance is vaporized.

Standard State Conditions are defined as:

• A set of conditions including 1 atm pressure, 25°C temperature, and 1 M concentration for solutions.

• The conditions at which all substances are in their gaseous state.

• A temperature of 0°C and 1 atm pressure for all reactions.

• The conditions where only solids are considered.

Find the enthalpy ΔfH of formation of butane given: ΔcH: C4H10(g) = -2877 kJmol⁻¹, C(s) = -394 kJmol⁻¹, H2(g) = -286 kJmol⁻¹.

• ΔfH (C4H10) = -126 kJmol⁻¹ (calculated using Hess's Law)

• ΔfH (C4H10) = -2877 kJmol⁻¹

• ΔfH (C4H10) = -394 kJmol⁻¹

• ΔfH (C4H10) = -286 kJmol⁻¹

Find ΔcH for the reaction: C3H8 + 5O2 → 3CO2 + 4H2O given: ΔfH: C3H8 = -104, CO2 = -394, H2O = -286 kJmol⁻¹.

• ΔcH = -2220 kJmol⁻¹ (calculated using Hess's Law)

• ΔcH = -2040 kJmol⁻¹

• ΔcH = -1560 kJmol⁻¹

• ΔcH = -980 kJmol⁻¹

Define enthalpy of formation. The enthalpy change when ______ from its constituent elements under standard conditions.

• one mole of substance is formed

• one mole of gas is decomposed

• two moles of substance are formed

• one mole of substance is combusted

Define enthalpy of combustion. The enthalpy change when ______ under standard conditions.

• one mole of substance reacts completely with oxygen

• one mole of substance is dissolved in water

• one mole of substance is formed from its elements

• one mole of substance is vaporized

What are the standard conditions for enthalpy changes?

• 298K and 100kPa

• 273K and 1atm

• 310K and 1atm

• 298K and 1atm

What is the enthalpy change of formation (ΔHf) for C4H10(g) if the enthalpy of combustion for C4H10(g) is -2877 kJ mol⁻¹, for CO2(g) is -394 kJ mol⁻¹, and for H2O(l) is -286 kJ mol⁻¹?

• -129 kJ mol⁻¹

• -2877 kJ mol⁻¹

• +129 kJ mol⁻¹

• -394 kJ mol⁻¹

Which formula is used to calculate the enthalpy change of formation (ΔHf) in the given example?

• ΔHf = [Sum of ΔHc products] - [Sum of ΔHc reactants]

• ΔHf = [Sum of ΔHc reactants] - [Sum of ΔHc products]

• ΔHf = [Sum of ΔHc reactants] + [Sum of ΔHc products]

• ΔHf = [Sum of ΔHc products] + [Sum of ΔHc reactants]