IIT/JEE Chemistry Practice #25: Enthalpy of Formation

The video tutorial covers the concept of enthalpy of formation, focusing on defining the standard enthalpy of formation and calculating enthalpy changes using standard heats of formation. It explains the criteria for standard heat of formation, such as reactants being elements in their most common form and forming one mole of the product. The tutorial also evaluates different reaction options to determine which comply with the definition of standard heat of formation and demonstrates how to calculate delta H for reactions using given heat of formation data.

What is the primary focus of the first question regarding enthalpy of formation?

• Understanding the concept of heat capacity

• Identifying the correct definition of standard enthalpy of formation

• Calculating the enthalpy change of a reaction

• Explaining the process of combustion

Which of the following is NOT a requirement for the standard heat of formation?

• Reactants must be elements in their most common form

• Formation of one mole of product

• Reactants can be compounds

• Elements must be in their most common allotrope

Why does the option with carbon in the diamond allotrope not qualify for standard heat of formation?

• Diamond is too expensive to use

• Diamond is not the most common allotrope of carbon

• Diamond is a compound, not an element

• Diamond is not reactive enough

Which option correctly represents the standard heat of formation for HF gas?

• Using hydrogen and fluorine as reactants

• Using diamond as a reactant

• Forming two moles of HF

• Using carbon monoxide as a reactant

What is the standard enthalpy change for a reaction calculated by?

• Multiplying the heats of formation of reactants and products

• Subtracting the heats of formation of reactants from products

• Subtracting the heats of formation of products from reactants

• Adding the heats of formation of reactants

What is the heat of formation value for elements used in reactions?

• Always positive

• Always negative

• Always zero

• Depends on the element

What is the calculated delta H value for the given reaction?

• 110.5 kilojoules per mole

• 393.5 kilojoules per mole

• 41.2 kilojoules per mole

• 241.8 kilojoules per mole