Name Date Titration of Samples \"a-f\" Summary Data Sheet Sample a Sample \"f\"
ID: 487034 • Letter: N
Question
Name Date Titration of Samples "a-f" Summary Data Sheet Sample a Sample "f" location (city, state): Sample "f source (e.g., surface water (SW); ground water (GW)) GW Sample initial pH 6.60 6.So vme- 10, SU NO Normality of H2SO, titrant N Notes: Provide volumes of H2SO4 titrant requested to the nearest 0.01 mL. v mL of acid titrant to reach the Phenolphthalein endpoint, Vimo mL of acid titrant from the Phenolphthalein endpoint to the Methyl Orange endpoint. Va3 8.3 mL of acid titrant to reach the pH 8.3 endpoint, V. mL of acid titrant from the endpoint to the V43 endpoint.Explanation / Answer
Solution:
To find the values of alkalinity due to OH- CO32- and HCO3- we need to follow up Table 2.
Given,
Table 1:- Analysis of water using phenolphthalein indicator Strength of H2SO4 solution = 2N
sample
a
b
c
d
f
Vp
5.9
6.3
0.3
10.15
0
Vmo
2.7
8.1
7.2
8.05
2.6
Table 2: To compare the phenolphthalein and methyl orange indicator readings while titration of sample water Vs standard acid solution.
Relation between Vp and Vmo
OH-
CO32-
HCO3-
Vp = 0
0
0
Vmo
Vp < Vmo/2
0
2Vp
Vmo– 2Vp
Vp = Vmo/2
0
2Vp
0
Vp > Vmo/2
2Vp-Vmo
2(Vmo– Vp)
0
Vp = Vmo
Vmo
0
0
So for sample, a: Vp > Vmo/2
Therefore, (i) Standard H2SO4 equivalent to OH- = 2Vp-Vmo mL and
(ii)Standard H2SO4 equivalent to CO32- = 2(Vmo– Vp)
Now,
(i) Normality of water sample (N1) w.r.t OH-
Water sample = Acid solution
N1V1 = N2V2
N1 = N2V2/V1 = 2(2Vp-Vmo)/V1
Hence, strength w.r.t OH- = 2(2Vp-Vmo)x17/V1 {where, 17 is the equivalent weight of OH-}
Also, strength w.r.t OH- as CaCO3 = strength w.r.t OH- x 17/50 g/L {since, 17 g OH- = 50 g CaCO3}
(ii) Normality of water sample (N1) w.r.t CO32-
Water sample = Acid solution
N1V1 = N2V2
N1 = N2V2/V1 = 2x2(Vmo-Vp)/V1
Hence, strength w.r.t CO32- = 4(Vmo-Vp)x30/V1 {where, 30 is the equivalent weight of CO32-}
Also, strength w.r.t CO32- as CaCO3 = strength w.r.t CO32- x 30/50 g/L {since, 30 g CO32- = 50 g CaCO3}
Similarly the strengths of the other samples viz. b, c, d, f can be calculated as above.
sample
a
b
c
d
f
Vp
5.9
6.3
0.3
10.15
0
Vmo
2.7
8.1
7.2
8.05
2.6
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