CHE 105 – Chemistry – Flashcards
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Unlock answers| Pressure |
| Force exerted per unit area by gas molecules as they strike the surfaces around them. |
| Common Units of Pressure |
Pa or Pascal (1 N/m2) = 101, 325 Pounds per square inch or psi = 14.7 Torr (1 mmHg) = 760 Inches of Mercury or in Hg = 29.2 Atmosphere or atm = 1 |
| What tool can be used to measure the pressure of a gas sample in lab? |
| Manometer |
| 4 basic properties of a gas sample |
Pressure (P) Volume (V) Temperature (T) Moles (m) |
| Boyle's Law |
An increase in volume or pressure results in a decrease of the opposite. ; Constant: Temp. ; moles P1V1=P2V2 |
| Charles's Law |
The volume of a gas increases with increasing temperature.
Constant: P & n V1/T1=V2/T2
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| Avogadro's Law |
When gas in a sample increases at constant temperature and pressure, its volume increases in direct proportion because the greater # of gas particles fill more space. ; Constant: T ; P V1/n1=V2/n2 |
| Ideal Gas Law |
The volume of gas is inversely proportional to the pressure of the gas. ; P = atm V = L Moles = mol Temperature = K |
| Molar Volume |
| Volume occupied by one mole of a substance. |
| STP |
Standard Temperature = 273 degrees Standard Pressure = 1 atm Standard Rate = 0.0821 Standard Volume = 22.4 L |
| Density of gas under standard conditions: |
| molar mass / molar volume |
| Density of gas is directly proportional to: |
molar mass. ; The greater the molar mass, the more dense the gas. ; Density (d = PM / RT) |
| Composition of dry air |
Nitrogen (N2) = 78% Oxygen (O2) = 21% Argon (Ar) = 0.9% Carbon Dioxide (CO2) = 0.04% |
| Partial Pressure |
(Pn) Pressure due to any individual component in a gas mixture. ; The sum of the partial pressure of the components in a gas mixture must equal the total pressure. (Ptotal) |
| Mole Fraction |
Xa;= na;/ ntotal ; number of moles of a component in a mixture divided by the total number of moles in the mixture |
| Hypoxia |
| Physiological condition developed due to low oxygen levels. |
| Vapor Pressure |
| Partial pressure of water in the mixture |
| Kinetic Molecular Theory |
1.) The size of a particle is negligibly small. 2.) The average kinetic energy of a particle is proportional to the temp. in kelvins. 3.) The collision of one particle with another is completely elastic |
Boyle's Law Kinetic Molecular Theory |
| If you decrease the volume of a gas, you force the gas particles to occupy a smaller space. Temp. remains same, number of collisions increases, resulting in greater pressure. |
Charles's Law Kinetic Molecular Theory |
| When you increase the temp. of a gas, the average speed and the average kinetic energy of the particles increases. Since greater kinetic energy results in more frequent collisions and more force per collision, the pressure of the gas increase if its volume is held constant. The only way for pressure to remain constant is for volume to increase. |
Avogadro's Law Kinetic Molecular Theory
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| When you increase the number of particles in a gas sample, the number of collisions with the surrounding surfaces increases. The greater number of collisions results in a greater overall force on surrounding surfaces. The only way for pressure to remain constant is for the volume to increase. |
Dalton's Law Kinetic Molecular Theory |
| The particles have negligible size and they do not interact. ;Particles of different masses have the same average kinetic energy at a given temperature, so they exert the same force upon collision with a surface. |
| Mean Free Path |
| The average distance that a molecule travels between collisions. |
| Diffusion |
| The process by which gas molecules spread out in response to a concentration gradient. |
| Effusion |
| Process by which gas escapes from a container into a vacuum through a small hole. |
| Thermochemistry |
| The study of relationships between chemistry and energy |
| Energy |
| The capacity to do work. |
| Work |
| The result of a force acting through a distance. |
| Kinetic Energy |
| The energy associated with the motion of an object. |
| Thermal Energy |
| The energy associated with the temperature of an object |
| Potential Energy |
| The energy associated with the position or composition of an object. |
| Chemical Energy |
The energy associated with the relative positions of electrons and nuclei in atoms and molecules. ; Also a form of potential energy. |
| Law of Conservation of Energy |
| Energy can be neither created nor destroyed. ;However energy can be transferred from one object to another and can assume different forms. |
| A good way to understand and track energy changes: |
| Define the system. |
| System Surroundings |
| Everything with which the system can exchange energy. |
| Energy Conversion Factors |
1 calorie (cal) = 4.184 J 1 Calorie (Cal or kcal) = 4184 J 1 kilowatt-hour (kWh) = 3.60x106;J |
| Internal Energy |
| The sum of the kinetic and potential energies of all of the particles that compose the system. |
| State Function |
| Value depends only on the state of the system, not on how the system arrived at that state. |
| Summarized Energy Flow |
-If the reactants have a higher internal energy than the products, deltaEsys;is negative and energy flows out of the system into the surroundings. ; -If the reactants have a lower internal energy than the products, deltaEsys;is positive and energy flows into the system from the surroundings. |
| Thermal Equilibrium |
| The heat transfer from an object to the surroundings stops when the two reach the same temperature. |
| Heat capacity is an extensive property because: |
1.) It's dependent on the amount of matter being heated.
2.) Water is more resistant to temperature change than steel. |
| Specific heat capacity |
| The measure of the intrinsic capacity of a substance to absorb heat. |
| Molar heat capacity |
| The amount of heat required to raise the temperature of 1 mole of a substance by 1 degree Celsius. |
| Pressure-Volume Work |
| Occurs when the force is caused by a volume change against an external pressure. |
| Bomb calorimeter |
| A piece of equipment designed to measure deltaE for combustion reactions. |
| Enthalpy |
| The sum of its internal energy and the product of its pressure and volume. |
| Endothermic Reaction |
| A chemical reaction with a positive deltaH that absorbs heat from its surroundings. |
| Enthalpy of Reaction or Heat Reaction |
deltaHrxn
Extensive Property |
| Relationships Involving deltaHrxn |
1.) If a chemical equation is multiplied by some factor, then deltaHrxn is also multiplied by the same factor. 2.) If a chemical equation is reversed, then deltaHrxn changes sign. 3.) If a chemical equation can be expressed as the sum of a series of steps, then deltaHrxn for the overall equation is the sum of the heats of reactions for each step. |
