Gen Chem 3 Exam 1 Flashcards

1
Q

When you are setting up a K expression, what goes in the numerator of the fraction?

A

The products

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2
Q

When you are setting up a K expression, what goes in the denominator of the fraction?

A

The reactants

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3
Q

When you are setting up a K expression, where do the exponents (if any) come from?

A

They are the coefficients from the balanced reaction

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4
Q

When you are setting up a K expression, what sort of chemicals should NOT be included in your calculation?

A

Solids and liquids (but DO include aqueous)

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5
Q

Kc has no units. But when you are calculating a Kc value with numbers, what units must those numbers have before you can plug them into the Kc formula

A

Kc is MOLARITY of products over reactants

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6
Q

Kp has no units. But when you are calculating a Kp value with numbers, what units must those numbers have before you can plug them into the Kp formula?

A

Kp is ATMOSPHERES of products over reactants (in this class.)

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7
Q

In the equation Kp = Kc(RT) ^ delta n, which R should you use: 0.08206 L atm mol^-1 K^-1 or 8.314 J mol^-1 K^-1 ? Both R values will be provided to you, but only one is correct to use.

A

0.08206 L atm mol^-1 K^-1

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8
Q

In the equation Kp = Kc(RT) ^ delta n how do you figure out the value of delta n?

A

moles of GAS products in the balanced reaction minus moles of GAS reactants in the balanced reaction

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9
Q

Products are generally favored. What must be true?

A

K > 1

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10
Q

Reactants are generally favored. What must be true?

A

K < 1

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11
Q

K > 1 means what in words?

A

Products are generally favored

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12
Q

K < 1 means what in words?

A

Reactants are generally favored

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13
Q

If, given the current conditions, a reaction will shift to form products, what must be true?

A

Q < K

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14
Q

If, given the current conditions, a reaction will shift to form reactants, what must be true?

A

Q > K

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15
Q

Q > K means what in words?

A

Given the current conditions, a reaction will shift to form reactants.

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16
Q

Q < K means what in words?

A

Given the current conditions, a reaction will shift to form products.

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17
Q

If you raise the temperature of an exothermic reaction, what happens?

A

The K value gets smaller. (And if it USED TO BE at equilibrium, the decrease in K will now make K less than Q, so it will shift to form reactants)

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18
Q

If you lower the temperature of an exothermic reaction, what happens?

A

The K value gets bigger. (And if it USED TO BE at equilibrium, the increase in K will now make K bigger than Q, so it will shift to form products)

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19
Q

If you raise the temperature of an endothermic reaction, what happens?

A

The K value gets bigger. (And if it USED TO BE at equilibrium, the increase in K will now make K bigger than Q, so it will shift to form products)

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20
Q

If you lower the temperature of an endothermic reaction, what happens?

A

The K value gets smaller. (And if it USED TO BE at equilibrium, the decrease in K will now make K less than Q, so it will shift to form reactants)

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21
Q

If you increase the molarity (or pressure) of reactants in the chamber, which way will it cause the reaction to shift?

A

It will try to use up those extra reactants. It will shift right to form products

22
Q

If you increase the molarity (or pressure) of products in the chamber, which way will it cause the reaction to shift?

A

It will try to use up those extra products. It will shift left to form reactants.

23
Q

If you decrease the molarity (or pressure) of reactants in the chamber, which way will it cause the reaction to shift?

A

It will shift left, using up products to try to recreate those missing reactants.

24
Q

If you decrease the molarity (or pressure) of products in the chamber, which way will it cause the reaction to shift?

A

It will shift right, using up reactants to try to recreate those missing products.

25
Q

A reaction begins at equilibrium. Which way will it shift if you increase the volume of the chamber

A

It will shift to make more of whichever side of the reaction has more gas.

26
Q

A reaction begins at equilibrium. Which way will it shift if you decrease the volume of the chamber?

A

It will shift to make more of whichever side of the reaction has less gas.

27
Q

When you flip a reaction, what should you do to its K value?

A

Take 1 over the old K value (1/K)

28
Q

When you multiply a reaction by a constant, what should you do to the K value?

A

Raise the K value to that constant. For instance, if you multiplied everything by 0.5, then the new K is the old K to the 0.5 power.

29
Q

When you sum up reactions, what should you do to their K values?

A

Multiply the K values together.

30
Q

You’ve encountered a tough flipping/summing up reactions problem. What are some good tips to try if you get stuck?

A
  • Save difficult chemicals for last.
  • If you currently have too MANY of a certain chemical as a product, you can fix that by getting some of that chemical as a reactant and canceling them out.
  • If you are having trouble getting the chemicals you NEED where you need them, instead try getting the chemicals you DON’T need to cancel out.
  • You don’t always have to use ALL the given reactions. Sometimes its best just to ignore one or more reaction.
31
Q

You’ve got a balanced reaction, and you’ve realized it is an ICE table problem. The coefficients in the balanced reaction should show up in TWO places in your work. Where are those two places?

A

The coefficients should show up in the change row of your ICE table.
The coefficients become exponents in your K expression.

32
Q

You’re doing an ICE table, and when you set up your K expression, you find that the math ends up being a “squared over a squared.” Algebraically, what is your next step?

A

Take the square root of both sides.

33
Q

What sort of units are you allowed to use in your ICE table?

A

You are always allowed to use moles.
You are allowed (and encouraged!) to use molarity whenever the volume is not changing and you have a Kc in the problem.
You are allowed (and encouraged!) to use atmospheres whenever the volume is not changing and you have a Kp in the problem.

(The temperature needs to be constant as well, but it will ALWAYS be constant in my ICE table problems.)

34
Q

Whenever samples are being MIXED or COMBINED, what is the safest unit to convert everything to?

A

mixing needs MOLES.

35
Q

H+ (aq) is the exact same thing as what?

A

H3O+ (aq). It is the exact same as hydronium ion

36
Q

What is the name of the OH- polyatomic ion?

A

Hydroxide

37
Q

What are ALL the eight strong bases? Yes, ALL of them. You can use a periodic table to help you.

A

LiOH
NaOH
KOH
RbOH
CsOH
Ca(OH)2
Sr(OH)2
Ba(OH)2

DON’T try to take a shortcut and say “anything with an OH on the end is a strong base.” Because things like Fe(OH)3 are NOT strong bases

38
Q

What are ALL the seven strong acids? Yes all of them. You can use a periodic table to help you.

A

HCl
HClO3
HClO4
HBr
HI
HNO3
H2SO4

DON’T try to take a shortcut and say that anything with an H out front is a strong acid. Because things like HF and H3PO4 are not strong acids.

39
Q

When you raise 10^-pH what do you get?

A

You get the MOLARITY of H3O+

40
Q

When you raise 10^-pOH what do you get?

A

You get the MOLARITY of OH-

41
Q

How do you go from molarity to moles?

A

Multiply by liters

42
Q

How do you go from moles to molarity?

A

Divide by liters

43
Q

How do you turn a pH into a molarity?

A

You raise 10^-pH to get the molarity of H3O+

44
Q

How do you turn a pOH into a molarity?

A

You raise 10^-pOH to get the molarity of OH-

45
Q

How do you take a molarity of H3O+ and turn it into a pH?

A

You take the negative log of the H3O+ molarity

46
Q

How do you take a molarity of OH- and turn it into a pOH?

A

You take the negative log of the OH- molarity.

47
Q

If you have the pH, how do you get the pOH?

A

pOH = 14 - pH

48
Q

You have the pOH, how do you get the pH?

A

pH = 14 - pOH

49
Q

You have a molarity of H3O+. How do you find the molarity of OH-?

A

Molarity of OH- = (10^ -14) / molarity of H3O+

50
Q

You are dealing with a problem that is mixing acids and/or bases. What is the FIRST step in the problem?

A

Identify which chemicals are acids (so moles of H3O+ matter)
and which chemicals are bases (so moles of OH- matter)

51
Q

In an acid/base problem, if pure water is added as one of the solutions, does that matter? And if so when/where.

A

It changes the total volume of the combined solution. That matters near the end of the problem when your total (or leftover) moles get turned back into a molarity.