Thermochemistry Concepts and Calculations

This video tutorial covers key concepts in thermochemistry, including internal energy, heat, and work. It explains how heat flows between systems and surroundings, and how work affects internal energy. The video provides examples of calculating changes in internal energy and discusses specific heat capacity and phase changes. It also covers balancing thermochemical equations, combustion reactions, and using Hess's Law to calculate enthalpy changes.

What is the sign of Q when heat is released from a system?

• Positive

• Undefined

• Negative

• Zero

If a gas expands from 2 L to 3 L at a pressure of 5 ATM, what is the sign of the work done by the system?

• Zero

• Negative

• Undefined

• Positive

How much energy is required to heat 50 grams of water from 25°C to 75°C?

• 20,920 J

• 2,615 J

• 5,230 J

• 10,460 J

What is the heat of fusion for water in kJ per mole?

• 4.184 kJ

• 6 kJ

• 18 kJ

• 12 kJ

In a combustion reaction, if 64 grams of oxygen reacts, how many kJ of heat energy will be released?

• 1,200 kJ

• 2,400 kJ

• 960 kJ

• 480 kJ

What is the enthalpy change when 3600 kJ of heat energy is released in a reaction?

• 99 grams of CO2

• 792 grams of CO2

• 198 grams of CO2

• 396 grams of CO2

What is the enthalpy of formation for CO2?

• 0 kJ/mol

• -393 kJ/mol

• -286 kJ/mol

• -785 kJ/mol

How do you calculate the enthalpy of a reaction using Hess's Law?

• Sum of reactants and products

• Sum of reactants minus products

• Sum of products minus reactants

• Difference between reactants and products

What is the enthalpy change for the reaction 2A + 2B → D + E using Hess's Law?

• 200 kJ

• 400 kJ

• 600 kJ

• 800 kJ

What is the purpose of using Hess's Law in thermochemistry?

• To measure the volume of gases

• To calculate the mass of reactants

• To determine the temperature change

• To find the enthalpy change of a reaction