NAME Determination of Total Water Hardness Prelab: Your instructor will stamp or
ID: 1046757 • Letter: N
Question
NAME Determination of Total Water Hardness Prelab: Your instructor will stamp or initial the prelab and have you attach it to your laboratory when you turn it in. Show neat detailed calculations for all results that required calculation. CHEM. 3A Section Number Initial or Stamp Answer the following questions based on the lab introduction and procedure: I. What is the goal of this experiment? 2 What are th umris f molarity M0? Express 0.001 10 M (Ca.. + Mg>, in those units What is the molarity of the EDTA standard you are using in this experiment? What is the chemical definition of water hardness? 2? 3. 4. 5. What affect does water hardness have on the concentration of soap? 6. What is the reaction ratio between ions responsible for water hardness and EDTA? 7. Draw a simple drawing of the set-up required for the titration of a water sample with EDTA to determine water hardness 8. What is signaled by the change of indicator color from burgundy to blue during the titration experiment? 9. During an EDTA titration, what solution goes into the buret and what goes into the Erlenmeyer flask? 10. A 25.0 mL sample of tap-water is titrated with 0.00500 M EDTA. 7.95 mL of EDTA is required for complete reaction with the water hardness in the 25.0 mL sample of tap water. What is the molarity of the total water hardness in the 25.0 mL sample? (no work no credit) RCC/CJV-2010Explanation / Answer
1 Aim of the experiment is to determine the total Hardness of the water sample using EDTA titration method
2 moles per litre
3 0.05 M of EDTA
4 The amount of dissolved calcium and Magnesium in the water is Total hardness of water
5 If the water is hard it will not form lather with soap solution whereas soft water forms good lather and hence cleans well
6 Ethylenediaminetetraacetic acid (edta) is a reagent that forms edta-metal complexes with many metal ions (but not with alkali metal ions such as Na+ and K+). In alkaline conditions (pH›9) it forms stable complexes with the alkaline earth metal ions Ca2+ and Mg2+. The edta reagent can be used to measure the total quantity of dissolved Ca2+ and Mg2+ ions in a water sample. Thus the total hardness of a water sample can be estimated by titration with a standard solution of edta.
7 refer internet for the set of this experiment
8 The change in colour tells that the unstable complex( Burgundy colour) forms satble Complex( blue Colour
9 0.05 M EDTA is taken in burette where as water sample + Buffer solution ( ammonia buffer) EBT indicator is taken in erlenmeyer flask
10 M1V1(EDTA)= M2V2 (WATER)
M1= 0.05 V1= 7.95 V2= 25 M2=?
M2 = 0.05 * 7.95 / 25 =0.159
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