Comprehensive Exam 3 Study Guide: Gas Laws and Thermochemistry

A set of vocabulary-style flashcards covering the key concepts, formulas, and laws for Chapters 5 and 6 of the Exam 3 Guideline.

Boyle's law

The relationship stating that the pressure and volume of a gas are inversely proportional at constant temperature, represented by the formula $P_1 V_1 = P_2 V_2$.

Charles's law

The relationship stating that volume is directly proportional to temperature at constant pressure, or pressure is directly proportional to temperature at constant volume, represented by $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ or $\frac{P_1}{T_1} = \frac{P_2}{T_2}$.

Ideal gas law

A fundamental gas equation used to determine gas behavior and to calculate density or molecular formula.

Dalton's Law components

Calculations involving partial pressure, mole fraction, and total pressure of a gas mixture.

Molecular speed distribution

The distribution of speeds among gas particles which is determined by temperature ($T$) and molar mass ($M$).

Avogadro's Law

A principle applied in gas stoichiometry calculations relating the volume of a gas to the number of moles.

Work ($w$)

Energy transfer resulting from gas expansion or compression, calculated using the formula $-P \Delta V$.

Internal Energy ($U$)

The total energy change of a system, defined by the sum of heat ($q$) and work ($w$) in the expression $U = q + w$.

Specific heat formula

The equation used to calculate heat energy based on mass ($m$), specific heat constant ($s$), and temperature change ($\Delta t$): $q = ms \Delta t$.

Hess's Law

A method used to calculate the enthalpy change ($\Delta H$) of a reaction by summing the enthalpy changes of individual reaction steps.

A Barometer measures _____________ pressure.

Atmospheric

A manometer (closed-tube) measures ____________ of interest.

the gas molecule

A manometer (open-tube) measures pressure of gas due to ____________________.

the atmosphere

Diffusion:

gradual mixing of molecules of one gas with molecules of another by their kinetic properties.

Effusion:

process that gas under pressure escapes from one compartment to another by passing through a small opening.

Ideal Gas Equation:

PV=nRT

Use the Ideal Gas Equation when ______________.

you have atleast 3 variables

An endothermic reaction “_________ _________” , has a _____ sign, and goes from ________ to system.

“feels cold”, +, surroundings

An exothermic reaction has a _______ sign, “______ _________", and the system ______ ______ heat to the surroundings.

+, “feels hot", gives off.

1st Law of Thermodynamics and the equation:

Energy cannot be created or destroyed, but converted from one form to another.

🔺U️=q+w

1st step to solve:

A rigid container of nitrogen gas is kept at 25.0°C and has a pressure of 1.50 atm. If the container is heated to 125.0°C, what is the new pressure?

Change C to K

Under what conditions is the heat flow of a system (q) exactly equal to its change in enthalpy (ΔH)?

Constant pressure

Calculate the standard enthalpy of combustion (ΔH°rxn) for one mole of liquid methanol (CH3OH):

2CH3OH(l) + 3O2(g) → 2CO2(g) + 4H2O(l)

Standard Enthalpies of Formation (ΔH°f):

● ΔH°f [CH3OH(l)] = -238.6 kJ/mol

● ΔH°f [CO2(g)] = -393.5 kJ/mol

● ΔH°f [H2O(l)] = -285.8 kJ/mol

What formula is used to solve?

The summation equation

ΔH°rxn = [2ΔH°f(CO2) + 4ΔH°f(H2O)] - [2ΔH°f(CH3OH) + 3ΔH°f(O2)]