Exam 1

Question 1

Flip a reaction…how does its K value change?

Answer 1

It inverts the K. Example: If the old K was 25, the new one is 1 / 25

Question 2

If you multiply all the coefficients in a reaction by 0.5, how does the K change?

Answer 2

The new K is the old K^0.5

Question 3

If you multiply all the coefficients in a reaction by 3, how does the reaction’s K value change?

Answer 3

The new K is the old K^3

Question 4

If you sum up reactions, how do you combine their K values?

Answer 4

The K values multiply. K-total = K1 * K2 * K3…etc

Question 5

Which value of R is used in the formula Kp = Kc(RT)^delta n? Is it the 8.314 one or the 0.08206 one?

Answer 5

0.08206 (L atm mol^-1 K^-1)

Question 6

What does the delta n mean in the formula Kp = Kc(RT)^delta n

Answer 6

Looking at the balanced reaction, and taking coefficients into account, delta n = # of GAS products - # of GAS reactants

Question 7

How do you convert Celsius into Kelvin?

Answer 7

Celsius + 273 = Kelvin

Question 8

What is the ideal gas law?

Answer 8

PV = nRT (Use Kelvin. Usually use 0.08206 as R)

Question 9

What goes on the top of the fraction when calculating K?

Answer 9

Products (the chemicals on the RIGHT hand side of the balanced reaction)

Question 10

What goes on the bottom of the fraction when calculating K?

Answer 10

Reactants (The chemicals on the LEFT hand side of the balanced reaction)

Question 11

What units go into a Kc calculation?

Answer 11

Molarity gets plugged in, but Kc itself has no units.

Question 12

A student has just calculated a K value by doing products over reactants.
Before they move on, what 3 common careless mistakes should they always check for?

Answer 12

Missing exponents
Accidentally putting solids or liquids into the K expression
Putting wrong units in (e.g. moles)

Question 13

A reaction begins at equilibrium. You then stress it by increasing the amount of reactants that are present. Which way does it shift?

Answer 13

It shifts to the RIGHT. It uses up those reactants and creates more products.

Question 14

A reaction begins at equilibrium. You stress it by removing products. Which way does it shift?

Answer 14

It shifts to the RIGHT to try to reform those missing products, and it uses up some of the existing reactants to do so.

Question 15

A reaction begins at equilibrium. You stress it by removing some reactants. Which way does it shift as a result?

Answer 15

It shifts to the LEFT to reform some of the missing reactants. It uses up some of the existing products to do so.

Question 16

A reaction begins at equilibrium. You stress it by putting some extra products into the chamber. How does the reaction shift?

Answer 16

It shifts to the LEFT to use up some of those excess products and make more reactants.

Question 17

A reaction that has some gasses in it begins at equilibrium. You stress it by increasing the volume of the chamber. Which way does the reaction shift?

Answer 17

It shifts to make more of whichever side of the reaction had MORE moles of GAS.

Question 18

A reaction that involves gasses begins at equilibrium. You stress the reaction by decreasing the volume. Which way does the reaction shift?

Answer 18

It shifts towards whichever side of the balanced reaction had FEWER moles of GAS.

Question 19

You increase the temperature of an exothermic reaction. How does its K value change?

Answer 19

It decreases.

Question 20

You increase the temperature of an endothermic reaction. How does its K value change?

Answer 20

It increases.

Question 21

You decrease the temperature of an exothermic reaction. How does its K value change?

Answer 21

It increases.

Question 22

You decrease the temperature of an endothermic reaction. How does its K value change?

Answer 22

It decreases.

Question 23

What does it mean when a reaction is “at equilibrium”

Answer 23

The forward rate equals the reverse rate, and so the chemical amounts present stop changing.

Question 24

What units can go into an ICE table?

Answer 24

Moles can always be used in an ICE table. Just be sure you change them to something else before using a K expression.

Molarity can be used whenever the volume is not changing and is the quicker way of solving a problem involving Kc

Pressure can be used whenever the volume (and temperature) is not changing and is the quicker way of solving a problem involving Kp

Question 25

What are all 7 of the strong acids? Yes ALL of them!

Answer 25

HI
HBr
HCl
HClO3
HClO4
HNO3
H2SO4

Question 26

What are all 8 of the strong bases. Yes, ALL of them!

Answer 26

Group one hydroxides; and calcium, barium, and strontium hydroxide.
LiOH
NaOH
KOH
RbOH
CsOH
Ca(OH)2
Ba(OH)2
Sr(OH)2

Question 27

When mixing chemicals, what unit do you need to try to get things into before summing them up or subtracting?

Answer 27

moles

Question 28

You have a molarity of H3O+ you want a pH. What do you do?

Answer 28

You take the negative log of the molarity.

Question 29

You have a molarity of OH-. How do you turn that into a pOH?

Answer 29

Take the negative log of the molarity.

Question 30

You have a pH. How do you turn it into a molarity of H3O+

Answer 30

Raise 10 to the negative pH

Question 31

You have a pOH. How do you convert it to a OH- molarity?

Answer 31

You raise 10 to the negative pOH

Question 32

You have a molarity of [H3O+] You want the molarity of {OH-]. What do you do?

Answer 32

[OH-] = 10^-14 / [H3O+]

Question 33

You have the molarity of [OH-] and you want the molarity of [H3O+]. What math do you do?

Answer 33

[H3O+] = 10^-14 / [OH-]

Question 34

You have the pH and you want the pOH. What math do you do?

Answer 34

pH = 14 - pOH

Question 35

You have pOH and want to find the pH. What math do you do?

Answer 35

pH = 14 - pOH

Question 36

When you are finding the pH or the pOH, you take the negative log of what unit?

Answer 36

It needs to be a molarity before you take the negative log.

Question 37

You’ve got the initial row of the ICE table filled in. How do you figure out which way the reaction will shift.

Answer 37

If any chemicals have “0” as their amount, you will be gaining those chemicals. But if its not that simple, you have to calculate Q and compare it to K.

Question 38

A reaction will SHIFT to form products. What must be true about Q and or K?

Answer 38

Q < K is the only correct answer.
(NOT K > 1. That just means products are generally FAVORED)

Question 39

A reaction will shift to form reactants. What must be true about Q and or K?

Answer 39

Q > K is the only correct answer.
(NOT K < 1. That just means that reactants are generally FAVORED)

Question 40

A reaction generally favors products. What must be true about Q and or K?

Answer 40

K > 1 is the only correct answer.
(NOT Q < K. That means that given the current conditions it will SHIFT to form products. But we don’t KNOW the current conditions, so we can’t predict a shift.)

Question 41

A reaction generally favors reactants. What must be true about Q and or K

Answer 41

0 < K < 1
(Not Q > K. That talks about SHIFTS, but this question asks about what is FAVORED)

Question 42

True or false: pH values must be between 0 and 14

Answer 42

False.

Question 43

Acidic solutions have what sort of pH values?

Answer 43

pH < 7

Question 44

Basic solutions have what sort of pH values?

Answer 44

pH > 7

Question 45

When you are mixing strong acids, what ion do you care about the most?

Answer 45

Hydronium (H3O+)

Question 46

When you are mixing strong bases, what ion do you care about the most?

Answer 46

Hydroxide ion (OH-)