Titration and Indicators Flashcards
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
litmus paper
red litmus paper turns blue = basic
blue litmus turns red = acid
common garden plant with flowers that come in many colors depending on the pH of the soil.
HYDRANGEA
blue flowers = SOIL IS ACIDIC
creamy white flowers = NEUTRAL
pink =BASIC
indicator that is produced from a substance that is naturally occurring or is itself a naturally occurring substance
NATURAL INDICATOR
Red beets, blueberries, and cranberries
are compounds created in a chemistry lab
SYNTHETIC INDICATORS
phenolphthalein
acid donates a proton and a
Bronsted-Lowry base accepts a proton
Bronsted-Lowry
two requirements for a substance to function as an acidbase indicator
- equilibrium affected by hydrogen ion concentration
- Two forms of the compound on opposite sides of the equilibrium must have different colors
the equilibrium between the protonated form and the anionic form is controlled by ———, SINCE THE INDICATOR IS A WEAK ACID.
HYDROGEN ION CONCENTRATION
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
(a) Universal indicator = Orange to orange-yellow (see table 2)
(b) Bromocresol Green = green (midway pH = 4.6)
(c) Phenol red = yellow
Phenolphthalein was colorless
Phenolphthalein was colorless, pH < 8.0
Bromocresol green was blue
Bromocresol green was blue, pH > 5.4
Methyl red was yellow
Methyl red was orange, pH > 6.2
Phenol red was yellow
Phenol red was yellow, pH < 6.4
a substance that changes color at a specific pH and is used to indicate the pH of the solution
INDICATOR
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.
(d) Not enough information is available
. 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.
b. 2.0
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.
. (b) The pH is between 4 and 5.
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.
(d) The pH is between 10.1 and 12.0.
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
. (a) Universal indicator = dark green
(b) Thymol blue = green (midway pH = 8.8)
(c) Methyl blue = blue
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?
(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
procedure where an acid is neutralized by a base (or vice versa) is known as
TITRATION
addition of a known concentration of base
(or acid) (also called the titrant ) to a solution of acid (or base) of unknown concentration
TITRATION
used to accurately dispense the volume of the solution of known concentration (either the base or the acid)
BURETTE
used to hold a known volume of the unknown concentration of the other solution (either the acid or the base)
ERLENMEYER FLASK
used to determine the endpoint of the titration
INDICATOR
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
equivalence point
to measure the changes in
pH as the titration goes from start to finish
pH meter
three types of titrations
(1) Strong acid vs. Strong base
(2) Strong acid vs. Weak base
(3) Weak Acid vs. Strong base
a graph of the pH
versus the volume of titrant added
titration curve
the solution of known concentration
titrant
purpose of initial titration
to determine, with as much accuracy as possible, the exact concentration of the solution in the burette
a solution whose concentration is known exactly
standard solution
Examples of chemicals used
to prepare standard solutions
- acidic potassium hydrogen phthalate, KHC7H4O4
- basic sodium carbonate, Na2CO3
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)?
0.180 mol/L
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?
12.5 mL
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.
0.1708 mol/L
