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Chem 30 > Unit 1 Thermodynamics > Flashcards

Unit 1 Thermodynamics Flashcards

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1
Q

What is enthalpy (ΔH)?

A

change in energy in a system

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2
Q

Do endothermic reactions require energy to proceed or do they release energy?

A

require energy to proceed

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3
Q

Do exothermic reactions require energy to proceed or do they release energy?

A

release energy

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4
Q

In endothermic reactions, is ΔH positive or negative?

A

positive

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5
Q

In exothermic reactions, is ΔH positive or negative?

A

negative

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6
Q

In endothermic reactions, which has less energy: the reactants or the products?

A

reactants

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7
Q

In endothermic reactions, which has more energy: the reactants or the products?

A

products

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8
Q

In exothermic reactions, which has less energy: the reactants or the products?

A

products

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9
Q

In exothermic reactions, which has more energy: the reactants or the products?

A

reactants

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10
Q

In endothermic reactions, is the enthalpy a reactant or a product?

A

reactant

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11
Q

In exothermic reactions, is the enthalpy a reactant or a product?

A

product

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12
Q

What is the reaction for photosynthesis?

A

6CO2(g) + 6H2O(l) –> C6H12O6(aq) + O2(g)

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13
Q

What is the reaction for cellular respiration?

A

C6H12O6(aq) + O2(g) –> 6CO2(g) + 6H2O(l)

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14
Q

What is this reaction called?

6CO2(g) + 6H2O(l) –> C6H12O6(aq) + O2(g)

A

photosynthesis

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15
Q

What is this reaction called?

C6H12O6(aq) + O2(g) –> 6CO2(g) + 6H2O(l)

A

cellular respiration

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16
Q

What is a combustion reaction?

A

A compound reacts with oxygen (burns) to give carbon dioxide (if the compound has carbon in it) and water (if the compound has hydrogen in it). If the compound has nitrogen or sulphur in it, NO2 and SO2 are also products.
ex. C3H8 + 5O2(g) –> 3CO2(g) + 4H2O(g)

17
Q

What are fossil fuels?

A

Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms (plants, animals, etc.), containing energy originating in ancient photosynthesis.

18
Q

Describe, in words, what photosynthesis is.

A

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms’ activities.

19
Q

Describe, in words, what cellular respiration is.

A

Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP) (i.e. mitochondria in cells turn sugar to energy)

20
Q

What is a calorimeter?

A

A calorimeter is a device that measures the heat (energy) of reactions. Based on how much water is in the calorimeter and how much the temperature increases/decreases after the reaction, the energy can be calculated (Q=mcΔt).

21
Q

Which elements are not singular in their elemental form?

A

H2, N2, O2, F2, Cl2, Br2, I2, P4, S8

22
Q

What is a catalyst?

A

a catalyst speeds up a reaction by providing an alternate pathway. a catalyst is not consumed by a reaction. a catalyst does not change the enthalpy (ΔH) of a reaction.

23
Q

What is an enzyme?

A

enzymes are biological catalysts (in organisms) that speed up reactions, are not consumed by the reaction and do not change the enthalpy (ΔH) of the reaction

24
Q

What is activation energy?

A

the minimum energy to start a reaction (energy barrier). both endothermic and exothermic reactions can require activation energy.

25
Q

What is a formation reaction?

A

reaction making a compound from its elements.

ex. 2H2 + O2 –> 2H2O

26
Q

What is a decomposition reaction?

A

a compound breaks down into its elements

ex. 2H2O –> 2H2 + O2

27
Q

What is the manipulated, controlled and responding variable of an experiment?
ex. testing different types of fuels in a calorimeter to see how much the energy release changes

A

manipulated (what is being tested): the different types of fuel
controlled (what stays the same): the calorimeter
responding (what changes due to the manipulated variable): how much energy is released/temp of the water

28
Q

What is Hess’ law?

A

ΔH(reaction) = ΔH(products) - ΔH(reactions)

  • The overall change in energy is the same whether the reaction occurs in one step or many steps
  • the net enthalpy change is the sum of the reactions combined to make the next reaction
29
Q

If you flip a reaction around (reactants -> products becomes products -> reactants), does the sign of ΔH change?

A

yes. When you flip a reaction with a -ΔH, it becomes positive and vice versa.

Chem 30 (7 decks)

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