EXPERIMENT NO. 02
OBJECT: To
determine the acidity of a given sample of water using N/50 Sodium Hydroxide
(NaOH) solution and Methyl Orange and Phenolphthalein as indicators.
OBSERVATION TABLE:
Titration between given water sample and N/100 sodium hydroxide solution and methyl
orange and phenolphthalein as
indicators.
S. No. |
Volume of sample (X) (mL) |
Burette reading (mL) |
Concordant reading (mL) |
|||
Initial |
Methyl Orange end point (Y) |
Phenolphthalein end
point (Z) |
Y |
Z |
||
1. |
20 |
0.0 |
5.8 |
13.6 |
5.8 |
13.6 |
CALCULATION:
Volume of given water
sample (X) = 20 mL
Volume of NaOH used up to methyl orange end
point = Y mL Volume of NaOH used up
to phenolphthalein end point = Z mL
1. Acidity up to Methyl orange endpoint:
According to the law of equivalence:
N1V1 of
Sample |
= N2V2 of NaOH |
N1 × 20 |
= N/50 × 5.8 |
N1 |
= 5.8/1000 |
Acidity up to the Methyl orange end
point (in terms of CaCO3 equivalent):
= Normality x Equivalent Weight of CaCO3
= (5.8/1000) x 50 g/L
= (5.8/1000) × 50 × 1000 mg/L or
ppm strong or mineral acidity =
290 ppm
2. Acidity up to Phenolphthalein
endpoint:
According to the law of
equivalence:
N1V1 of
Sample |
= N2V2 of NaOH |
N1 × 20 |
= N/50 × 13.6 |
N1 |
= 13.6/1000 |
Acidity up to the Phenolphthalein (in terms of
CaCO3 equivalent):
= Normality x Equivalent Weight of CaCO3 = (13.6/1000) x 50 g/L = (13.6/1000) × 50 × 1000 mg/L or ppm
Total acidity
= 680ppm
Now,
Weak acid acidity = Total
acidity - Mineral acid acidity
RESULT: Acidity of given water sample:
Total acidity =680 ppm
Strong acid acidity = 290 ppm
Weak acid acidity=390 ppm
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