Thermodynamics and Energy Calculations

These flashcards cover the key concepts related to thermodynamics, energy calculations, and calorimetry based on the lecture notes.

What does the First Law of Thermodynamics state?

Energy cannot be created or destroyed; it can only be transferred or changed in form.

What is the equation for the work done by a piston?

w = -PAV, where P is pressure, A is area, and V is the change in volume.

What is the formula used to calculate enthalpy change (ΔH)?

ΔH = Hproducts - Hreactants.

How much heat is evolved for the production of 1.00 mole H2O in the given reaction?

286 kJ of heat is released.

How do you calculate the total heat evolved when 4.03 g of hydrogen reacts with excess oxygen?

Calculate moles of H2 (4.03 g / 2.016 g/mol) and multiply by -286 kJ.

What is a key characteristic of a state function like enthalpy?

A change in enthalpy does not depend on the pathway taken between two states.

What happens to the temperature of the surroundings in an endothermic reaction?

The temperature of the surroundings decreases.

In the context of calorimetry, what is the relationship between qsys and qsurr?

qsys = -qsurr; what happens to the surroundings is the opposite of what happens to the system.

How is q (heat) calculated in calorimetry?

q = mCΔT, where m is mass, C is specific heat capacity, and ΔT is the change in temperature.

What does Hess's Law state about reaction energy?

The energy change of a reaction is the same regardless of the pathway taken.

What is the standard state for a gas?

A pressure of exactly 1 atm.

What is ΔH° for a reaction?

ΔH° reaction = ΣΔH° (products) - ΣΔH° (reactants).

What is the significance of the sign change when a reaction is reversed?

The magnitude of ΔH remains the same, but the sign changes.

How do you calculate ΔH from standard enthalpies of formation?

ΔH reaction = ΣΔHf (products) - ΣΔHf (reactants).

What is the molar heat capacity of N2O at 298 K?

30.38 J K⁻¹ mol⁻¹.

What is the average kinetic energy equation for ideal gases?

KE_avg = RT, where R is the universal gas constant and T is the temperature in Kelvin.