Chapter 18/ Chapter 19 Concepts

Question 1

Predict the pH of a titration given the type of acid and base (strong or weak)

Answer 1

Strong: from start of titration to near endpoint, pH increases slowly –> just before and after equivalence point pH increases rapidly –> at equivalence, moles acid = moles base and solution is neutral (salt)

Weak: initial pH is higher than strong –> pH changes near equivalence point are more subtle –> pH > 7 at equivalence point due to formation of basic salt

Question 2

Use a titration curve to identify what type of titration was employed (e.g.
weak acid plus strong base)

Answer 2

look at pH where curve starts and steepness and what pH equivalence point is at

Question 3

Distinguish between endpoint and equivalence point

Answer 3

equivalence point: point at which moles of acid = moles of base
endpoint = point in titration where the indicator changes color

Question 4

Select an indicator given the acid and base species used in a titration

Answer 4

look at pH range of where indicator works in comparison to pH of equivalence point

Question 5

Define solubility product constant (Ksp)

Answer 5

measures the extent to which a substance will dissolve in water (salt and dissolved ions reach equilibrium)

Question 6

Cite examples of how the following can affect solubility: common ions and pH

Answer 6

common ions: decreases the solubility of a weak electrolyte when present (from strong electrolyte)

pH: basic anion is more soluble in acidic solution, acidic cation is more soluble in basic solution

Question 7

Define key electrochemical terms: galvanic cell, anode, cathode and salt bridge

Answer 7

galvanic cell: an electrochemical cell where a spontaneous redox reaction occurs to produce electrical energy

anode: the electrode at which oxidation occurs

cathode: the electrode at which reduction occurs

salt bridge: keeps the two half-cells connected and allows ions to flow between them

Question 8

Describe the conditions used to calculate the standard reduction potential for a reaction

Answer 8

all solutes are 1 M and all gases are at 1 atm, temperature is 25 C

Question 9

Explain what an electrochemical cell is and how it works

Answer 9

electrons leave the anode and flow through the wire to the cathode

as electrons leave anode, the cations formed dissolve into the solution in the anode

as electrons reach the cathode, cations in the cathode are attracted to the now negative cathode

the electrons are taken by the cation, and the neutral metal is deposited on the cathode

salt bridge prevents charge imbalance –> anions move towards anode and cations move towards cathode

Question 10

Define concentration cell

Answer 10

cells where the cell potential is generated entirely by a difference in concentration at the two electrodes (same ions in anode and cathode)