HChem Test Chapter 17 Flashcards
When solving an equilibrium equation (think lab) make sure to…
Make the side losing the heat negative (make sure answer makes sense
What is the equation to find Qwater
Mass * 4.184 * delta T
What is the equation to solve for an equilibrium with a metal
Mass(m)Cp(m)delta T(m)=Mass(w)4.184deltaT(w)
Heat lost by metal=
Heat gained by water (make -)
When solving an equation, make sure your units ______
Agree (kJ, mole, Kelvin for Gibbs)
When doing heat of formation, make sure that the thing being combusted has a coefficient of ____
These are _________
1
Combustion
What is the typical combustion equation
__+O2—>CO2+H2)
What is Hess’s Law
Regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes
What is the summation equation
Sum of all products’ heat of formation-sum of all the reactants’ heat of formation
(Multiply by coefficients)
If you are asked to calculate the heat of combustion for butane for a specific compound, make that compound’s coefficient ____
1
Don’t do this is asked to find the heat of reaction for the entire process
If energy is being added on product side, the reaction is _____
If energy is being added on reactant side, the reaction is _____
Exothermic
Endothermic
Positive delta S means _______
More disorder
If something needs a continuous energy supply, it is most likely ____
Endothermic
An ____ reaction produces energy as it proceeds
Exothermic
What is the “direction” or trend most chemical reactions move toward in terms of energy and disorder
Lower energy, higher disorder
Delta H stands for ___
Delta S stands for ___
Delta G stands for __
Enthalpy
Entropy
Gibbs
What is the formula for Gibbs
Delta G=delta H-(T*deltaS)
T must be in kelvin
-delta G is ____
Spontaneous
If a reaction is spontaneous it does not need _____ help
Outside (catalyst)
The heat content of the activated complex of any reaction is the ___ to the _____
Bottom, top
The heat content of anything (reactants, products, AC) is ____
How talk it is (y axis)
Name 4 things that will speed up or slow down a chemical reaction
Concentration, temperature, catalyst, surface area
When drawing a graph, label the _____ and give it a ____
Axes, title
- heat is equal to __________
Heat released (you can say either/or)
When finding a limited reactant, what do you do
Go from grams of the reactant to grams of the product
Whichever is less is limiting reactant
When doing dimensional analysis, remember that if the element is diatomic, factor that into ____
Molar mass
qH2O=___
-qrxn
What is the Hf value for elements
0 (they are naturally occurring and no heat is absorbed)
Delta H =
qrxn/moles
When doing enthalpy calorimetry and finding final temperature, what do you do
Set enthalpy =qrxn/moles, find moles, cross multiply to find qrxn, turn it negative and set equal to mass, Cp, and Tf-Ti
1.00 ml of water=
1.00 g of water
When doing specific heat equation, put temp in ___
C
What is the second law of thermodynamics
Changes in the universe tend towards a state of greater disorder
More moles to less moles is __ delta S
-
The tendency for all reactions is to have __delta H and __ delta S
-,+
The equation for the delta Hf of N2O is:
N2(g)+3/2O2(g)—>N2O3(g)
Disorder is ___ delta S
+
The equation for Hf is not _______, but you write the equation for one mole of the compound asked
Summation
The equation for the delta Hf of any molecule always contains either __ or ___
02 or H2
Delta H must be in ___
kJ/mol
