6.6 - 6.8 Quiz Flashcards
What does the little circle by delta H indicate?
That we are in standard state
1 mol, 1 atm, and 298 K(unless stated otherwise)
On this quiz, what should you always make sure to do with chemical equations?
You need to make sure they are balanced
Bond energies should always be…
a) positive
b) negative
POSITIVE
_________ bonds requires energy and _________ bonds releases energy.
Breaking; Forming
If heat energy is released, what is the sign on the q value?
Negative
Bond order
Amount of bonds there are
ex: double bond, triple bond, etc.
If heat energy is absorbed, what is the sign on the q value?
Positive
How do you calculate the energy released or absorbed using bond enthalpies?
You do Bonds Broken Minus Bonds Formed.
“Basket Ball is My Best Friend”
How do you find the enthalpy of formation?
Products minus reactants
If the enthalpy of reaction(delta H) is negative, which side of the chemical equation does it go on?
It goes on the right side; The product side
If you are just given an element like O in a bond enthalpy question what do you do?
Assume that it’s bond enthalpy is 0 and basically ignore it.
How are bond order and bond energies related?
The higher the bond order, the higher the bond energy
Ex: a triple bond will have the highest bond energy
If an equation says “Calculate the heat evolved”, will the equation be negative or positive?
It will be negative because evolved means heat is released to the surroundings
If the enthalpy of reaction(delta H) is positive, which side of the chemical equation does it go on?
It goes on the left side; The reactant side
If you are given a problem where they present the moles for both reactants, what type of problem will it be? And how would you solve it?
It is a limiting reactant problem and you solve it by turning both into heat and the greater number will be the correct answer.
What happens to the bonds of reactants in a chemical equation?
They are broken
What should you do if bonds repeat themselves on both sides of a bond enthalpy question?
They cancel out
What is important to remember with the stoichiometry equations?
LOOK AT SIGNS, but remember that you can’t have negative moles, only negative heat
What is the enthalpy of formation for all things in their pure, standard state?
0
You are stranded and have two plastic jugs, you decide to burn one of the jugs to to send smoke signals and to keep yourself warm, and you decide to save the other jug to carry and store water. One jug is
made out of polyvinyl chloride (PVC) and one is made out of polypropylene (PP). Which jug do you
choose to burn and why?
You would choose the one that has a higher heat value(positive or negative, but the largest number), because that would mean it gives off the most heat per mole produced meaning that the smoke signal would last longer.
What happens to the bonds of products in a chemical reaction?
They are formed
