the alkalinity for each water sample. Show your calculations. Summarize
the data in a figure?
Total alkalinity (mg/L as CaCO3) = A × N × 50000
total titrant (mL)
5000= conversion factor to change normality into units of CaCO3
alkalinity =0.0325L × 0.02 mg/L × 50000
= 650 mg/L
A= 14.5 mL
50 mL =0.05L
alkalinity = 0.0145L ×0.02mg/L × 50000
Unknown Water Sample-
N= 0.02 mg/L
50 mL= 0.05L
alkalinity = 0.0012L ×0.02mg/L × 50000
is one source of error for this analysis and how can it be avoided?
this analysis is very much easy to perform, but in terms of error, some points
we should keep in mind to avoid error,
1. the too
much fast addition of the sulfuric acid may cause to skip the exact reading.
stopcock and tip of the burette should be filled to get right reading because
one or two drops can make a big difference.
of delivery tip should be always under the solution being titrated.
rinsing of the burette with acid can also effect the calculation of alkalinity.
on your knowledge of the chemistry of different sources of water, explain the
differences in alkalinity that you found. Where the results what you expected?
Comment on the unknown water sample. Where might this water source have come
3. The water
collected or usually present at different sources called as surface water
always have different range of the alkalinity as the water comes from rocks or
ponds usually will have high alkalinity as the carbonate, bicarbonate and
hydroxide ions from those rocks joins water. The results are very much close to
my expectations. As the range of alkalinity of surface water is high.
ground water passes from sandstone and granite will have low alkalinity, the
expected value of the alkalinity of groundwater is low as in my lab I
sample provided to us to calculate the alkalinity had very low alkalinity and I
guessed it could be the rain water, I was not exactly right but it was snow
that turned to water at room temperature.
4.You are working in a lab that routinely does
alkalinity analyses. You usually buy
0.02 N sulfuric acid from Hach, but this time your boss orders pure sulfuric
acid from Sigma-Aldrich. You have to
make 5 L of 0.02 N sulfuric acid to do a series of alkalinity titrations. Describe how you would make the
solution. Show all calculations.
The Normality of sulfuric acid = 0.02N
required = 5L
mass of sulfuric acid= 49g
compound needed (in grams) = 0.02 × 49 × 5 = 4.9g
acid required = grams of acid needed
Conc. % × specific gravity
gravity is known as, 1.84 and concentration of sulphuric acid is 97%
0.97 × 1.84
Explain how alkalinity is different from hardness.
is ability of a solution to neutralize the acids such as bicarbonates,
carbonates and hydroxide ions.
is sum of multivalent metal ions present in solution.
it is expressed as the concentration of calcium carbonate ions in water.
it also expressed the concentration of CaCO?.
alkalinity comes from limestone and dolomite dissolved in water as it passes
from rocks, but the calcium part causes hardness of water.
whereas the carbonate part causes alkalinity of water.
This have vital effect on toxicity caused by copper (used to treat algae and
parasites) in water.
it should be minimum as for development of species of fish that originates in
6. What is the difference between
phenolphthalein alkalinity and total alkalinity?
is measure of only hydroxides and half carbonates. It aslo called as
is determined by amount of bicarbonate, carbonate and cyanurate ions.
titrate the water sample with acid titrant to phenolphthalein end point is
called phenolphthalein alkalinity.
is ability of water to resist a pH change.
should be known to determine carbonate alkalinity.
is used a key parameter in the maintenance of balance of water.
this the phenolphthalein changes color at pH 8.2 – 8.3..
total alkalinity is important as it helps to keep pH stabilised around 4.2- 4.5.
for total alkalinity is
(?OH- – H+?) +
HCO3- + 2 CO3-2
for total alkalinity is
– H+?) + CO3-2 – H2CO3*
is alkalinity important for drinking water treatment? What might happen to the
treatment processes if the alkalinity of the water was low? How would this
7. Ans :- The presence of hydroxides, bicarbonates and
carbonates present in water cause alkalinity. Bi carbonates among these ions
has biggest effect on alkalinity of water. The high alkalinity will change the
taste of water as soda water,
The limit of alkalinity in water is limited by EPA
drinking water regulations in terms of TDS (total dissolved solids) is 500ppm
and in terms of PH is should be around 7.
of alkalinity: –
1.The alkalinity is very much important for aquatic
animals as it saves them from damage which can be done by rapid change occur in
2.In the coagulation high alkalinity will cause
formation of floc and flocculation also can be effected by alkalinity change as
this will cause to make water more heavier by binding of the destabilized
particles by coagulation.
While water suffering low alkalinity we should treat
it by neutralizing filter, in this process we add neutralising material to
raise pH of water. But it may cause a problem of hardness in water as the use
of magnesium oxide to raise pH of water but also hardness. To get rid of this
we should backwash the neutralising filter time to time and also the
installation od cartridge filter prior to neutralising filter will remove
solids from water. By doing so neutralising filter will work for long time. The
water softener should be used to remove hardness. We also have to keep in mind
that use of sodium as softener may not be suitable for people need low sodium
diet. We can alternatively use soda ash and sodium hydroxide which will not
cause hardness and will raise the pH and make it neutral.
The acid injections also help to neutralise water and
minimises the chances of pipe corrosion.