Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Thermochemisty terms
| Term | Definition |
|---|---|
| ΔH | -The change in enthalpy for a reaction/process -The heat absorbed/released by a system (q) under constant pressure |
| What are the four ways to calculate/measure ΔH? | 1- Calorimetry 2- Standard enthalpies of formation 3- Hess's law 4- Bond enthalpies |
| Bond enthalpies | - Sum of bond enthalpies broken - sum of bond enthalpies formed= ΔH -can ONLY be used when all reactants and products are in their gaseous phases; average energy used to break the bond of ONE isolated molecule free from any IMF's -Often less accurate |
| Hess's Law | -States that ΔH for a rxn is a state function; independent of the pathway taken - the sum of enthalpy changes in intermediate rxns will equal the unknown enthalpy change of the whole rxn -DEPENDENT on molar ratio and direction (apply to individual ΔH) |
| Enthalpy of formation | The energy associated with the formation of 1 mol of a compound from its respective reactants in their MOST STABLE STATES under standard pressure tells us the chemical energy associated with 1mol of a compound -enthalpiesofproducts-enthalpiesofreactants |
| Calorimetry (experimental method) | - ΔH=q=mcΔT - in cases where there is a phase change, conduct all q calculations and add together to get final q - q1+q2+q3+q4+q5= q reaction= ΔH |
| ΔT | - (Tfinal-Tinitial) -Change in temperature of a reaction -measurement of heat |
| Specific heat capacity (c) | - Energy required to raise the temp of 1 g of a substance by 1c - varies depending on the COMPOSITION of an element (mass is taken in to account by being specific) -an INHERENT VALUE of a particular substance, changes depending on phase of the substance |
| Enthalpy of vaporization | - The amount of energy needed to convert 1g of a substance from a liquid to a gas at a constant temp and pressure, overcoming IMFS - same for condensation but negative - an INHERENT PROPERTY of a substance -q4/m |
| Enthalpy of fusion | - The amount of energy needed to melt 1g of a substance from a solid to a liquid, overcoming bonds in lattice structure - an INHERENT PROPERTY depending on IMFS same for freezing but negative - q2/m |
| Vaporization/condensation | endothermic/exothermic |
| Melting/freezing | endothermic/exothermic |
| q water = -[ q metal] | When heat is being transferred from one substance to another, take hot metal in water, the energy LOST by the metal is EQUAL to the energy GAINED by the water -metal is negative because it is LOSING ENERGY, water is positive because it is GAINING ENERGY |
Created by:
NoodlyFella