6.1-6.3 Quiz Flashcards
If the surroundings is pushing on the system and compressing a piston, the work is …..
Positive
What does an endothermic reaction profile look like?
The products are higher in energy than the reactants
How is the energy between the system and the surrounding connected according to the first law of thermodynamics?
The first law of thermodynamics states that energy cannot be created or lost, only transferred. So energy of the system= - energy of the surroundings.
The negative side will go on whatever is LOSING energy
How do you find the activation energy for a reverse reaction?
You do Top of the graph- products
Dissociation; would this be an endothermic or exothermic process?
Breaking up larger compounds into smaller ones
This would be endothermic because the system NEEDS energy to break up the compounds so it is absorbing energy
What phase changes are related to exothermic reactions?
Changes that involve combining materials.
Freezing
Condensation
Deposition
When the energy of a system decreases what type of reaction is it?
Exothermic
If an equation is talking about a change in temperature, what are they referencing?
THE SURROUNDINGS
When products are higher than reactants what does that mean about the stability of the products?
The products are less stable
E (subscript a) or activation energy
The energy necessary to start a reaction. They are used to break bonds or IMFs in the reactants.
Electron Affinity; would this be an endothermic or exothermic process?
The amount of energy released when an electron is added(electron on left side of equation) ; Exothermic because energy is being released
If the system is pushing on the surroundings and expanding a piston, the work is …..
Negative
Work
Energy needed to move something against a force. Think about expanding gases pushing on a piston
Universe
System and surroundings together
How do you label the coordinates for an energy profile?
The x axis is reaction coordinate and the y axis is potential energy
Surroundings
everything else around the system
How do you answer the questions that ask for justification and ask you to choose the BEST answer?
Look for causation and not js correlation
Also on this quiz look for answers that talk specifically about breaking or forming bonds.
Vaporization vs boiling
Liquid to vapor
vs
Liquid to gas
Catalysts
Increase reaction rate and are not consumed in the reaction. They also provide lower activation energies.
Words related to exothermic reactions
Exiting
Losing
Releasing
Negative
Sublimation
Solid to gas
Ionization energy; would this be an endothermic or exothermic process?
Energy required to remove an electron(electron on right side of equation)
This would be endothermic because the system NEEDS energy so it will be absorbing energy
If you are told to draw a reaction pathway and are given the reactants and the activation energy(ex: reactants- 40 kJ and Ea- 50 kJ), then how do you graph this?
The reactants will be at 40 and the Ea will be at 90 kJ, because you do 40 plus the Ea.
Condensation
Gas to liquid
Describe how heat flows with systems and surroundings for an endothermic reaction.
The system gains(or absorbs) energy from the surroundings.
System
The part of the world that you are studying. Typically a chemical reaction
When the energy of a system increases what type of reaction is it?
Endothermic
What does an exothermic reaction profile look like?
The products are lower in energy than the reactants
A solution of ammonium nitrate was created by dissolving 5.02 grams of ammonium nitrate in
100.0 mL of water at 22.3°C. After forming the solution the temperature was 17.3°C.
Did heat enter the system or leave the system?
What is the sign for q?
Was the dissolution process endothermic or exothermic?
Entered the system
Positive
Endothermic
This is because the system is ammonium nitrate and the surroundings are everything else. The water’s temperature decreases because the system absorbs its heat which is why this process is endothermic.
How do phase changes affect kinetic energy?
They don’t. Going from solid to liquid to gas, the temperature remains constant and the average kinetic energy stays the same
Heat(q)
- Units
Amount of thermal energy transferred from something that is hotter to something that is colder.
Units are J or kJ.
Words related to endothermic reactions
Positive
Increase
Absorb
Deposition
Gas to solid
Describe how heat flows with systems and surroundings for an exothermic reaction.
The system loses(or releases) energy and it is gained by the surroundings.
What phase changes are related to endothermic reactions?
Changes that involve breaking/ separation
Melting
Boiling
Vaporization
Sublimation
What does a catalyst due to the enthalpy?
NOTHING, it is not affected by it.
Work equation
- P delta (V)
P= pressure in atm
Delta V is the change in volume
The lower the activation energy, the ____________ the rate of reaction
Faster
What part of a reaction energy profile is new bonds being formed?
When the energy is released, when the graph is dropping
How does temperature affect average kinetic energy and speed?
Particles in a warmer body will typically have a higher average kinetic energy and speed.
However, if you are comparing two elements, the smaller element will have a greater speed regardless.
Thermal equilibrium
When the average kinetic energy and temperature of both bodies are the same
Heat transfer/ Heat exchange/ Transfer of energy as heat
When hotter particles and colder particles collide, energy is transferred between them. The hotter particles lose some energy and the colder particles gain some energy.
How is heat always transferred?
From the HOTTER substance to the COLDER substance
In terms of what occurs at the particulate level, explain how the temperature of water increases after an alloy sample is added.
The atoms in the alloy transfer kinetic energy to the molecules in the water
What occurs at the particulate level when the water and the alloy reach thermal equilibrium?
At equilibrium the average kinetic energy of the atoms in the alloy is equal to the average kinetic energy
of the water molecules
What is happening on a heating curve when the temperature is constant, and what is happening when the temperature is increasing?
Constant- IMFs are being overcome and average kinetic energy and temperature are constant
Increasing- Average kinetic energy and temperature are increasing
What is the heat calculation with phase changes?
Mass times enthalpy change
Which enthalpy change are you looking for with phase changes when they reference freezing and melting?
Fusion
What temperature does water melt at and what temperature does water boil at?
Melt- 0 degrees celsius
Boil- 100 degrees celsius
How do you answer phase change questions like this: How much energy does it take to heat 50.0 g of water at 25.0°C to steam at 107.0°C?
You have to use multiple steps and add them all together.
Ex: 1) Heat water, 2) Water to gas(because the question says steam), 3) Heating gas(because it says 107)
Water to gas is the only one where you do mass times enthalpy change and you would do mass times delta H of vaporization
Which enthalpy change are you looking for with phase changes when they reference boiling and steam, condensing and vaporizing?
Vaporization
What happens to the temperature of something as it undergoes a phase change?
It remains constant
