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Chemistry > Thermochemistry > Flashcards

Thermochemistry Flashcards

1
Q

What is energy?

A

Ability to do work or transfer heat

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2
Q

What does work do?

A

Energy used to cause an object that has mass to move.

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3
Q

What does heat do?

A

Energy used to cause the temperature of an object to rise.

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4
Q

What is a system?

A

the molecules we want to study (thing you want to study

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5
Q

What are the surroundings?

A

are everything else

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6
Q

What is the first law of thermodynamics?

A

the total energy of the universe is a constant; if the system loses energy, it must be gained by the surroundings, and vice versa.

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7
Q

What is an open system?

A

can exchange both matter and energy with an outside system.

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8
Q

What is a closed system?

A

exchange energy but not matter with outside system

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9
Q

What is an isolated system?

A

Can exchange neither energy or matter with outside

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10
Q

What is the second law of thermodynamics?

A
  • energy can be transferred as heat
  • Heat flows from warmer objects to cooler until thermal equilibrium
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11
Q

What is Q?

A

the amount of energy required to raise the temperature of a substance by 1 Celsius

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12
Q

What is c?

A

the amount of energy required to raise the temperature of 1 g of a substance by 1 K.

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13
Q

What is internal energy (E)?

A

the sum of all kinetic and potential energies of all components of the system

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14
Q

What is enthalpy?

A

total heat content of a system

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15
Q

What is endothermic?

A

heat being absorbed

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16
Q

What is exothermic?

A

Heat being released

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17
Q

Why do some energy not let temperature rise?

A

Some of the energy is used to change in states

18
Q

When water turns into steam, why is it at the same temperature for a long time?

A

Because the bonds are being broken

19
Q

What is Hess’s Law?

A

“If a reaction is carried out in a series of steps, ΔH for the overall reaction will be equal to the SUM of
the enthalpy changes for the individual steps.”

20
Q

What is bond dissociation?

A

energy needed to break one mole of the bond to give separated atoms - everything being in the gas state

21
Q

How to measure reaction rate?

A

Anything over time (depletion of reactant or formation of products)

22
Q

How to measure concentration?

A
  1. Change in volume
  2. remove small samples of a reaction mixture and perform titration
  3. use of a spectrophotometer
  4. Measure remaining mass
23
Q

What increases rates of reaction?

A
  1. as concentration of reactants increase
  2. as temp increased
  3. with a catalyst -> lower activation energy
  4. as reactant surface area increases
24
Q

What is the average rate?

A

Reaction rate over time

24
Q

What is the average rate?

A

Reaction rate over time

25
Q

What is instantaneous rate?

A

Reaction rate at any given time

26
Q

What makes an effective collision?

A
  1. correct geometry
  2. sufficient energy (being absorbed or released)
27
Q

What is activation energy?

A

Minimum amount of kinetic energy the reactants must have in order to react.

28
Q

What affects the reaction rate?

A
  1. Nature of Reactants
  2. Concentration
  3. Temperature
  4. Catalyst
  5. Surface Area (Particle Size)
  6. Mixing (Stirring)
29
Q

How does the nature of reactants affect rate?

A

Some reactants are more reactive than others

30
Q

How does concentration affect rate?

A

Higher concentration = more collisions

31
Q

How does temperature affect rate?

A

Higher temperature means faster collisions

32
Q

How does catalyst effect rate?

A

Lowers the activation energy

33
Q

How does particle size affect the rate?

A

Smaller the particle size = faster the rate

34
Q

What is rate law?

A

how changes in the amount of a substance affect the rate of a chemical reaction

35
Q

What does rate law tell us?

A
  • shows the relationship between the reaction rate and the concentrations of reactants
  • k is a constant that has a specific value for each reaction.
  • The value of k is determined experimentally
  • Exponents tell the order of the reaction with respect to each reactant.
36
Q

What are elementary steps?

A

A reaction intermediate (or, reactants) is converted into the next reaction intermediate (or, products)

37
Q

What is a reaction’s molecularity defined by?

A

the number of particles that participate as reactants in an elementary step.

38
Q

Rate law vs overall rate law

A

Rate law: for all the steps (1 each)
Overall rate law is for the whole overall reaction
- Gives the R.D.S

39
Q

What is the reaction mechanism?

A

sequence of actual events that take place as reactant molecules are converted into products

Chemistry (16 decks)

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