Titration and Indicators

Question 1

a paper that has been dipped in a substance that will undergo a color change when it is dipped in either an acid or a base

Answer 1

litmus paper

red litmus paper turns blue = basic
blue litmus turns red = acid

Question 2

common garden plant with flowers that come in many colors depending on the pH of the soil.

Answer 2

HYDRANGEA

blue flowers = SOIL IS ACIDIC
creamy white flowers = NEUTRAL
pink =BASIC

Question 3

indicator that is produced from a substance that is naturally occurring or is itself a naturally occurring substance

Answer 3

NATURAL INDICATOR

Red beets, blueberries, and cranberries

Question 4

are compounds created in a chemistry lab

Answer 4

SYNTHETIC INDICATORS

phenolphthalein

Question 5

acid donates a proton and a
Bronsted-Lowry base accepts a proton

Answer 5

Bronsted-Lowry

Question 6

two requirements for a substance to function as an acidbase indicator

Answer 6

• equilibrium affected by hydrogen ion concentration
• Two forms of the compound on opposite sides of the equilibrium must have different colors

Question 7

the equilibrium between the protonated form and the anionic form is controlled by ———, SINCE THE INDICATOR IS A WEAK ACID.

Answer 7

HYDROGEN ION CONCENTRATION

Question 8

If the pH of the solution is 4.8, what would be the color of the solution if the following indicators were added?

(a) Universal indicator
(b) Bromocresol Green
(c) Phenol red

Answer 8

(a) Universal indicator = Orange to orange-yellow (see table 2)
(b) Bromocresol Green = green (midway pH = 4.6)
(c) Phenol red = yellow

Question 9

Phenolphthalein was colorless

Answer 9

Phenolphthalein was colorless, pH < 8.0

Question 10

Bromocresol green was blue

Answer 10

Bromocresol green was blue, pH > 5.4

Question 11

Methyl red was yellow

Answer 11

Methyl red was orange, pH > 6.2

Question 12

Phenol red was yellow

Answer 12

Phenol red was yellow, pH < 6.4

Question 13

a substance that changes color at a specific pH and is used to indicate the pH of the solution

Answer 13

INDICATOR

Question 14

If you had an acid-base neutralization reaction that turned phenolphthalein pink and Thymolphthalein blue, what is the pH of the solution?

(a) 8.2
(b) 9.4
(c) 10
(d) Not enough information is available.

Answer 14

(d) Not enough information is available

Question 15

. If you had an acid-base neutralization reaction that turned methyl violet blue and Thymol blue orange,
what is the pH of the solution?

a. 1.6
b. 2.0
c. 2.8
d. Not enough information is available.

Answer 15

b. 2.0

Question 16

Universal indicator is an indicator commonly used in the laboratory. At a pH of 6 it is pale yellow and at
a pH of 4 it is pale orange. If the indicator was orange, which statement would be definitely true?

(a) The solution is probably acidic.
(b) The pH is between 4 and 5.
(c) The solution is probably basic.
(d) The pH is less than 5.0.

Answer 16

. (b) The pH is between 4 and 5.

Question 17

Alizarin Yellow R is an indicator that changes color in the pH range from 10.1 to 12.0. Below 10.1 the
color is Yellow, above 12.0 the color is red. If the color of the solution containing Alizarin Yellow R was orange,
which statement about the solution would be true?

(a) The pH is below 10.
(b) The pH is above 12.0.
(c) The solution is definitely acidic.
(d) The pH is between 10.1 and 12.0.

Answer 17

(d) The pH is between 10.1 and 12.0.

Question 18

If the pH of the solution is 8.9, what would be the color of the solution if the following indicators were
added?

(a) Universal indicator
(b) Thymol blue
(c) Methyl blue

Answer 18

. (a) Universal indicator = dark green
(b) Thymol blue = green (midway pH = 8.8)
(c) Methyl blue = blue

Question 19

A solution has been found in the laboratory that was tested with a number of indicators. It was found that
the following indicators showed these results:

(a) Phenolphthalein was colorless
(b) Orange IV was yellow
(c) Universal indicator was orange
(d) Methyl orange was red
What was the pH of the solution?

Answer 19

(a) Phenolphthalein was colorless, pH < 8.0
(b) Orange IV was yellow, pH > 3.0
(c) Universal indicator was orange, pH = 3-4
(d) Methyl orange was red, pH < 3.2
Therefore the pH of the solution must be between 3.0 and 3.2, should be pH = 3.1

Question 20

procedure where an acid is neutralized by a base (or vice versa) is known as

Answer 20

TITRATION

Question 21

addition of a known concentration of base
(or acid) (also called the titrant ) to a solution of acid (or base) of unknown concentration

Answer 21

TITRATION

Question 22

used to accurately dispense the volume of the solution of known concentration (either the base or the acid)

Answer 22

BURETTE

Question 23

used to hold a known volume of the unknown concentration of the other solution (either the acid or the base)

Answer 23

ERLENMEYER FLASK

Question 24

used to determine the endpoint of the titration

Answer 24

INDICATOR

Question 26

the point where the number of moles of acid exactly equals the number of moles of base | a calculated point in the neutralization of the acid SA) and the base

Answer 26

equivalence point

Question 27

to measure the changes in pH as the titration goes from start to finish

Answer 27

pH meter

Question 28

three types of titrations

Answer 28

(1) Strong acid vs. Strong base (2) Strong acid vs. Weak base (3) Weak Acid vs. Strong base

Question 29

a graph of the pH versus the volume of titrant added

Answer 29

titration curve

Question 30

the solution of known concentration

Answer 30

titrant

Question 31

purpose of initial titration

Answer 31

to determine, with as much accuracy as possible, the exact concentration of the solution in the burette

Question 32

a solution whose concentration is known exactly

Answer 32

standard solution

Question 33

Examples of chemicals used to prepare standard solutions

Answer 33

* acidic potassium hydrogen phthalate, KHC7H4O4 * basic sodium carbonate, Na2CO3

Question 34

What is the concentration of sodium hydroxide when 32.34 mL is required to neutralize a solution prepared by dissolving 1.12 g of KHC7H4O4(s) in 25.00 mL of H2O(L)?

Answer 34

0.180 mol/L

Question 35

When 10.0 mL of a 0.125 mol/L solution of hydrochloric acid, HCl, is titrated with a 0.100 mol/L solution of potassium hydroxide, KOH, what is the volume of the hydroxide solution required to neutralize the acid? What type of titration is this?

Answer 35

12.5 mL

Question 36

Calculate the concentration of hypochlorous acid if 25.00 mL of HClO is used in a titration with 32.34 mL of a 0.1320 mol/L solution of sodium hydroxide.

Answer 36

0.1708 mol/L