Lab # 06 Determination of Water Acidity PDF

11/5/2024 Environmental Engineering (CEE 350) LAB# 06 Determination of Water Acidity Instructor: Dr. M. T. Amin Email: [email protected], Office#2075, Building#11 To deTermine The acidiTy of Given waTer sample...

11/5/2024 Environmental Engineering (CEE 350) LAB# 06 Determination of Water Acidity Instructor: Dr. M. T. Amin Email: [email protected], Office#2075, Building#11 To deTermine The acidiTy of Given waTer sample 2 1  11/5/2024 THEORY Acidity of water is its quantitative capacity to neutralize a strong base to a designated pH. It is measure of amount of base required to neutralize a given sample to specific pH. Acidity thus depends upon end point pH or indicator used. Dissolved CO2 is usually major acidity component of unpolluted surface water According to method of determination, acidity is important because acid contributes to corrosiveness and influences 3 certain chemical and biological processes. SIGNIFICANCE Acidity present due to free carbon dioxide has no significance from public health viewpoint, but water containing mineral acidity are unacceptable. Acidic waters pose corrosion problem and interfere in water softening and water treatment process. For biological treatment of wastewater, pH must be between 6 and 9.5. Hence, highly acidic waters require adjustment of pH before treatment. 4 2  11/5/2024 PRINCIPLE Mineral acidity is measured by titration to a pH of about 4.5 using methyl orange as indicator. The carbon dioxide acidity present in the sample can be neutralized completely by titration to pH of 8.3 using phenolphthalein end point which 5 measures both mineral and CO2 acidity Required Apparatus & Solutions NaOH Solution 6 3  11/5/2024 PROCEDURE (Mineral acidity) i) Take 50ml of sample (VS) in a conical flask and add 2 drops of methyl orange indicator. ii) If solution turns green/blue, methyl orange acidity is absent. iii) If it turns faint orange color, titrate with 0.02N NaOH, which is in Burette until color changes to yellow. iv) Note down volume of titrant (VA). Mineral Acidity (mg/L as CaCO3) = (VAN/VS) x 50000 7 VA = volume of NaOH in mL, N = Normality of titrant, VS = volume of sample PROCEDURE (Total acidity) i) Take 50ml of sample (VS) in a conical flask and add 2 drops of phenolphthalein indicator. ii) Initially, solution will be colorless. iii) Titrate with 0.02N NaOH until appearance of pink color. iv) Note down volume of NaOH (VB). Total Acidity (mg/L as CaCO3) = (VBN/VS) x 50000 8 VB = volume of NaOH in mL, N = Normality of titrant, VS = volume of sample 4  11/5/2024 Results (Mineral acidity) Sample Trial Initial reading (mL) Final reading (mL) NaOH added (VA, mL) 1 Lab sample 2 3 1 Tap water 2 3 𝑚𝑔 9 𝑪𝑶𝟐 𝒂𝒄𝒊𝒅𝒊𝒕𝒚 ( 𝑎𝑠 𝐶𝑎𝐶𝑂3) = 𝑇𝑜𝑡𝑎𝑙 𝑎𝑐𝑖𝑑𝑖𝑡𝑦 − 𝑚𝑖𝑛𝑒𝑟𝑎𝑙 𝑎𝑐𝑖𝑑𝑖𝑡𝑦 𝐿 Results (Total acidity) Sample Trial Initial reading (mL) Final reading (mL) NaOH added (VB, mL) 1 Lab sample 2 3 1 Tap water 2 3 Sample Unit Total Acidity Mineral Acidity CO2 acidity 10 Lab sample Mg/L as Tap water CaCO3 5