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Gen Chem 3 > Exam 4 Flash Cards > Flashcards

Exam 4 Flash Cards

1
Q

You have just been told that a compound is being oxidized. What does that mean?

A

It is LOSING electrons. Some atom in the compound is having its OXIDATION STATE GO UP.

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2
Q

You have just been told that a compound is being reduced. What does that mean?

A

It is GAINING electrons. Some atom in the compound is having its OXIDATION STATE GO DOWN.

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3
Q

The side of the electrochemical cell where oxidation happens is called what?

A

The anode.

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4
Q

The side of the electrochemical cell where reduction happens is called what?

A

The cathode.

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5
Q

Electrons flow from which side of the electrochemical cell to which other side?

A

They always flow from anode to cathode.

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6
Q

Positive ions in the salt bridge head towards which side of the electrochemical cell?

A

Towards the cathode (to cancel out the negative charge of the electrons that were headed there.)

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7
Q

Negative ions in the salt bridge head towards which side of the electrochemical cell?

A

Towards the anode (to replace the charge it lost when it gave up electrons)

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8
Q

The chemical that causes a DIFFERENT chemical to be oxidized is called the what?

A

Oxidizing agent.

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9
Q

The chemical that causes a DIFFERENT chemical to be reduced is called the what?

A

Reducing agent.

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10
Q

An element all by itself with no charge has what oxidation state?

A

0

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11
Q

A single atom with a charge on it has what oxidation state?

A

Whatever the charge is.

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12
Q

Except for peroxides, when oxygen is in a compound with other atoms, what is the oxidation state of the oxygen?

A

Negative 2

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13
Q

In this class, when hydrogen is found in a compound along with another element, what is the oxidation state of the hydrogen?

A

Positive 1. (There do exist compounds where hydrogen is negative 1, but I won’t ask you those)

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14
Q

When in a compound with other types of atoms, what is the oxidation state of fluorine?

A

Negative one.

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15
Q

If you sum up the oxidation states of every atom in a substance what does it equal?

A

It equals the overall charge of the substance. If the substance in question wasn’t an ion, then it equals zero.

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16
Q

What are the steps for balancing reactions with the redox method in base?

A

1) Split up the reaction into two half reactions (one oxidation, one reduction)
2) Balance all elements that are not H or O
3) Balance oxygen with water
4) Balance hydrogen with H+
5) Balance charges with electrons
6) Combine the two half reactions in such a way that the electrons perfectly cancel
7) However many H+ was in that (acidic) answer, add that many OH- ions to BOTH sides.
8) Turn H+ and OH- into water on the one side of the equation that they both show up.
9) Simplify your answer to the smallest whole number coefficients if needed.

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17
Q

You have found two standard reduction half reactions from the big table. How do you combine them properly?

A

Flip the anode’s reaction and its sign, then add them up. Do not multiply them by anything.

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18
Q

In electrochemistry, what does the “n” variable mean when it shows up in equations like the Nernst equation?

A

It is how many electrons got canceled out in each of the half reactions when they were combined.

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19
Q

What is the formula to find Q in the Nernst equation?

A

Products over reactants. Don’t forget your exponents. Solids and liquids don’t show up (but aqueous does)

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20
Q

You are working a kinetics problem where the temperature changes in the middle of the problem. What equation will you need?

A

You will need the Arrhenius equation. There are three versions that all work, but you’ll probably prefer the one with the Ln( k2 / k1) in it.

21
Q

You are working a kinetics problem that involves TIME. And it doesn’t ask for a rate. What sort of equation will you need?

A

An integrated rate law.

22
Q

How do you calculate a rate with a table of molarities and times?

A

Rate = Change in molarity / Change in time

23
Q

You have a table of initial molarities and initial rates. What do you solve for first?

A

You write the blank rate law, pick two rows off the table where only one molarity is changing, and use the magic of MATH to solve for the exponents (orders)

24
Q

In kinetics, what does the word “order” mean?

A

It is the exponent on that chemical in the rate law. The overall order is the sum of all the exponents.

25
Q

In a kinetics problem, the same data is plotted 3 different ways on 3 different graphs. Each graph has time as its x axis but something different as the y axis. How do you use these graphs to solve for the order and the rate constant?

A

On these graphs, the rate constant will be the absolute value of the slope. The graph to pay attention to is the only one where the data forms a line. The y axis of that graph will tell you what order the reaction was:
Molarity = 0th order
Ln(Molarity) = 1st order
1/Molarity = 2nd order

26
Q

You see a plot of Ln(k) vs. 1/T. How do you use the equation of its best fit line to solve for Ea or to solve for the pre-exponential term?

A

Ea = -8.314 * slope.
Pre-exponential term = e^(y intercept)

26
Q

You see a plot of Ln(k) vs. 1/T. How do you use the equation of its best fit line to solve for Ea or to solve for the pre-exponential term?

A

Ea = -8.314 * slope.
Pre-exponential term = e^(y intercept)

27
Q

You are given a half-life of a first order reaction. What is a good first step to do?

A

Turn the half-life into a rate constant with Half life = 0.693 / k

28
Q

What value of R should you use in the Arrhenius equation?

A

8.314 J / (mol K) (not 0.08206 L atm / (mol K) )

29
Q

How would you set up the math to solve for the exponent in this algebra?
3.37 ^ b = 129

A

b = Ln(129) / Ln (3.37) = 4

30
Q

What is the symbol for a positron?

A

An “e” with a 0 for its top number and a positive 1 for its bottom number.

31
Q

In nuclear chemistry, what is the symbol for an electron?

A

An “e” with a 0 for its top number and a negative 1 for its bottom number.

32
Q

Electrons and positrons are what sort of particles?

A

Beta particles

33
Q

What is an alpha particle

A

It is two protons and two neutrons bound together. Its symbol is He with a 4 on top and 2 on the bottom.

34
Q

What is the symbol for a gamma particle

A

It is the Greek letter gamma (that looks like an upside down charity ribbon) with a zero as its top number and a zero as its bottom number.

35
Q

Spontaneous nuclear decay reactions are always which order?

A

First.

36
Q

What is “the trick” to solving the sorts of carbon dating problems I like to ask?

A

Treat any rate that is provided as if it were a molarity and plug it into the first order integrated rate law.

37
Q

Fusion in nuclear chemistry means what?

A

Combining two nuclei together.

38
Q

Fission in nuclear chemistry means what?

A

Splitting apart a (parent) nucleus ion to one or more (daughter) nuclei. Often there are multiple daughters, but if one of the products is SIGNIFICANTLY larger than the other, the main larger product is the only one called the daughter.

39
Q

What are the steps to calculate a binding energy per nucleon of an atom, given its isotope and mass?

A

1.) Make sure everything is in kg
2.) Write a reaction where the atom breaks up into its individual nucleons
3.) Do products – reactants with the masses to find the mass defect
4.) Use E = mc2 to convert the mass defect into energy
5.) Divide by the # of nucleons.

40
Q

When I ask you to fill in the missing particle in a nuclear reaction and insist that you show two simple equations as your work, what am I looking for?

A

That the sum of the top numbers is the same on both sides of the reaction. (Conservation of total # of nucleons)

And that the sum of the bottom numbers is the same on both sides of the reaction (conservation of charge)

41
Q

What is the symbol for a neutron?

A

The letter “n” with 0 as its bottom number and positive 1 as its top number.

42
Q

When a particle is “captured” or a particle is “absorbed into the nucleus” which side of the balanced reaction does it go on?

A

It goes on the reactants side.

43
Q

When a particle is emitted or produced, which side of the reaction does it go on?

A

The products side.

44
Q

What can E-standard be converted into using only a balanced reaction and no other info?

A

It can be converted into delta G standard or into K

45
Q

What do you do to an E-standard value when you do the following things to its reaction?
1) Flip the reaction.
2) Multiply the reaction by 4
3) Sum up the reaction with a different reaction

A

1) Flip the sign of E-standard
2) Do nothing to E-standard
3) Add this E-standard to that other one.

46
Q

What do electrochemists call a reaction that spontaneously forms products?

A

Galvanic or Voltaic

47
Q

What do electrochemists call reactions that do not spontaneously form products

A

Electrolytic

Gen Chem 3 (4 decks)

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