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Coggle Second Semester - Mohammed Shaik P2 (Thermochemistry (Energy…
Coggle Second Semester - Mohammed Shaik P2
Empirical
Percent Composition
Step 1) First find the molar mass of the compound
Percent composition is the term used to describe the percent by mass of each element in a compound.
Step 2) To find Percent composition of the element in the compound you simply take the molar mass of the element and divide it by the compunds molar mass and multiply by 100.
Ex: MgCO3
Molar Mass of entire compound: 24.31+ 12.01+3(16.00) = 84.32g
Mg: (24.31 x 84.32) x 100 = 28.83%
Molecular Formula: the true number of atoms of each element in the formula of a compound
Molecular Formula : (empirical)n
Ex: C6H6 = (CH)6
Rhyme:
1) Percent to mass 2) Mass to Mole 3) Divide by Small 4) Multiply till whole
USE WHEN EVERYTHING ADDS UP TO 100
Combustion Analysis
Amount of Oxygen
Do not assume 100 grams are given
Must know mass of unknown substance before burning
Usually produces carbon dioxide, water, and nitrogen compound
Gas
Pressure
1 atm = 101.3 kPa
1 atm = 760 torr
1 atm = 760 mm Hg
May need to convert to STP using these conversions when solving if it asks for STP or in atm
Ideal Gas Law
Ideal Gases are imaginary gases that perfectly fit all of the assumptions of the kinetic molecular theory
Pressure is due to to the collisions of the gas particles with the walls of the container
No Kinetic energy is lost in collisions
Gases with the lowest molecular weight will have the highest average
PV=nRT where P is pressure, V is volume, n is moles, R is gas constant and T is temperature
Thermochemistry
The calorie is the heat required to raise the temperature of 1 gram of water by 1 Celsius degree
The Joule is the SI system for measuring heat
1 Joule = 1 Newton x Meter = 1kg x mg^2/s^2
Energy
Heat(Enthalpy) Change Delta H: The amount of heat energy released or absorbed during a process
Thermal Energy
Kinetic Energy
Potential Energy
Endothermic: Absorbing energy
Exothermic: releasing energy
Specific Heat: The amount of heat required to raise the temperature of one gram of substance by one degree Celsius
Use Formula: q = MC(AT) where M is the mass, C is the specific heat capacity and AT is the change in temperature, and q is Heat lost of gained
Latent Heat of Phase Change: The energy that must be absorbed in order to convert one mole of solid to liquid at its melting point (6.01 kJ/mol or 333 J/g)
Heat of Vaporization (Molar or in grams): The energy that must be absorbed in order to convert one mole of liquid to gas at its boiling point (40.7 kJ/mole or 2240 J/g)
Temperature remains constant during phase change
0 to -real numbers are ice; heat of fusion at 0 Celsius; water t 0 to 100 C; heat of vaporization at 100 C; 100+ C is steam
Calorimetry: The amount of heat absorbed by a release of a chemical change that can be measured usually by change in temperature at a known quantity of water
MCAT = -[MCAT]
Boyle's Law
P1V1=P2V2
Gay Lussac's Law
P1T1=P2T2
Charles Law
V1T1=V2T2
STP
P = 1 atm
T = 0 degrees Celsius, 273 Kelvins
Standard Pressure and Temperature
Molar volume of an ideal gas is 22.42 liters at STP