Measurement of Ph Using Indicators

This document discusses the measurement of pH using indicators. It explains the concept of acid-base indicators and their role in determining pH. The document also provides an experimental section and discusses the results obtained. The discussion includes the pH values of different solutions and their classification as acids or bases. References and appendix with ionic equations are also provided.

Running head: MEASUREMENT OF PH USING INDICATORS 1
Measurement of Ph Using Indicators
Name of Student
Institution Affiliation

MEASUREMENT OF PH USING INDICATORS 2
Introduction
Background
In their scholarly work, Chemistry Education Research and Practice, Cartrette & Mayo,
states that, “An acid-base indicator is a chemical species that changes color at a specific pH as
the pH (acidity) of the solution is varied.” However, Bronsted and Lowery describes the
interaction between acids and bases with regards to the transfer of protons between the chemical
species. It describes an acid as that which can give out a proton H+, while a base as that which
can accept a proton (Cartrette & Mayo, 2011). Further, the acid, structure-wise is that chemical
which must contain a hydrogen atom, whereby it will thus dissociate it in the form of an ion. The
on Bronsted and Lowery theory is significant as it helps in the description of acid-base reactions
in any solvent (Cooper et al., 2016). Some examples which justify the theory includes
Fig1: Bronsted and Lowery equations, (Brawner, 2015).
Besides, the weak acids and bases form the acid-base indicators. They have a ph ranges
either close to the neutral ph., for a weak acid, or further from the ph., for a weakly basic

MEASUREMENT OF PH USING INDICATORS 3
solution. They act as indicators since the color of both the acid form of the indicator is not
similar to the basic form of indicator (Cartrette & Mayo, 2011).
Objectives
 To understand how to use indicators to test the ph
 To understand the difference between acids and bases.
Experimental Section
By using deionized water, five small test tubes were rinsed and dry them. 1ml of 0.1 M
HCl was then added to each of the test tubes. All the tests tubes were labeled to be sure of the
indicator added. To each of the test tubes, one of the seven indicators in the table was then
added. By means of observation, a comparison of the colors in each test tube was made and
recorded down. This will help in determining the 0.1M HCl ph., within one ph. Unit (Orgován &
Noszál, 2011). The observed color as well as the possible ph. range of the indicator solution was
as well noted. The application of the remaining solutions then repeated the same procedure. For
instance, H2O CH3COONa, HCl, CH3COOH, Na2CO3, NH3, Al2(SO4)3, and Unknown
solution. The quantity was maintained at 0.1 M. Finally; the obtained results were recorded in a
clean datasheet (Laboratory-manual)
Results
Table 1. Solutions tested
TB BPB BCG BCP BTB PR AY pH
H2O Olive Purple Green Yucky
red
Light
olive
Orang
e
Yellow 7.0
CH3COON
a
Diarrhe
a color
Bright
purple
Blue Dark
purple
Dark
green
Bright
orange
Yellow 8.5
HCl Ruby
red
Yellow Orange Yellow Orange Orang
e
Orange 1.0
CH3COOH Bright
orange
Diarrhe
a color
Yellow
-orange
Yellow Orange Orang
e
Scramble
d egg
2.9

MEASUREMENT OF PH USING INDICATORS 4
Na2CO3 Dark
blue
Purple Light
blue
Purple Blue Pink Blood red 11.
1
NH3 Dark
blue
Purple Blue Purple Deep
blue
Pinky
rose
Orange 11.
0
Al2(SO4)3 Sunrise
orange
Deep
dark
green
Olive Sunset
orange
Orange Light
orange
Dark
orange
3.5
Unknown Yellow Bright
purple
Deep
blue
Diarrhe
a
Light
diarrhe
a
Orang
e
Yellow 6.5
The left axis represents the solutions used to perform the pH experiment. The last solution used
was an unknown solution number 73. The top axis represents pH ranges of selected indicators.
Discussion
1) Distilled water, pH 7.0, the experimental results and the obtained one on the ph. of
distilled water are similar. It indicates that water is a neutral solution. This shows that my
experiment was accurate.
2) 0.1 M Sodium acetate, pH 8.6 - the experimental results and the obtained one on the ph.
of sodium acetate differed slightly. The percentage error is 11%. The solution is a strong
base.
3) 0.1 M HCl, pH 1- the experimental results and the obtained one on the ph. of
hydrochloric acid was similar with no percentage error. The solution is a strong acid. This
shows that my experiment was accurate.
4) 0.1 M Acetic acid, pH 2.9- the experimental results and the obtained one on the ph. of
acetic acid was similar with no percentage error. The solution is a strong acid. This shows
that my experiment was accurate.

MEASUREMENT OF PH USING INDICATORS 5
5) 0.1 M Sodium carbonate, pH 11.3- the experimental results and the obtained one on the
ph. of sodium carbonate differed slightly. The percentage error is 0.01%. The solution is
a strong base. This shows that my experiment was slightly accurate.
6) 0.1 M Ammonia, pH 11.1- the experimental results and the obtained one on the ph. of
ammonia differed somewhat. The percentage error is 0.009%. The solution is a strong
base. This shows that my experiment was slightly accurate.
7) 0.1 M Aluminum sulfate, acidic pH 3- the experimental results and the obtained one on
the ph. of sodium acetate differed slightly. The percentage error is 16.7 %. The solution is
an acid.
8) The unknown solution was found to have a ph. of 6.5; it is likely to be a weak acidic
solution. This is because solutions having a ph. range closer to 7 are termed as weak
acids.

MEASUREMENT OF PH USING INDICATORS 6
References
Brawner, B. (2015). Artist as Chemist [10th grade].
Cartrette, D. P., & Mayo, P. M. (2011). Students' understanding of acids/bases in organic
chemistry contexts. Chemistry Education Research and Practice, 12(1), 29-39.
Cooper, M. M., Kouyoumdjian, H., & Underwood, S. M. (2016). Investigating students’
reasoning about acid–base reactions. Journal of Chemical Education, 93(10), 1703-1712.
laboratory manual fall 2018 and spring 2019 edition, Chemistry 104 department of chemistry

MEASUREMENT OF PH USING INDICATORS 7
APPENDIX
Ionic Equations
I. H2O
H+(aq)+OH-(aq)→H2O(l)
II. CH3COONa
CH3COO- + H2O <--> CH3COOH + OH-
III. HCl
HCl (aq) --> H+ (aq) + Cl- (aq)
IV. CH3COOH
CH3COOH (aq) + OH- (aq) → CH3COO- + H2O (l)
V. Na2CO3
2 H+ (aq)+ CO3−→H2O (l)+ CO2↑
VI. NH3
H+(aq) + NH3(g) -> NH4+(aq)
VII. Al2(SO4)3
2Al3+(aq) + 6OH- (aq)= 2Al(OH)3(aq)