Please explain in depth and more on concepts needed to understand a question lik
ID: 637624 • Letter: P
Question
Please explain in depth and more on concepts needed to understand a question like this about water hardness- studying for an exam
Show ALL Work For Full Credit! Please write multiple choice answers in the space provided 3. A new company, started by two Purdue engineers, decided to capitalize on the mistaken belief that zinc is an effective agent for fighting the common cold by makinga soap from the 1:1 reaction of palmitic acid and Zn(OH)2. Unfortunately the soap had poor cleaning properties, and caused severe skin irritation. What mistakes did the company make in their product3(12pts)Explanation / Answer
Hardness is that characteristics of water by which it can prevent the formation of lather/foam with soap solution.
Also defined as the soap-consuming capacity of water.
Presence of certain salts of Ca, Mg and other heavy metal ions like Al3+ , Fe3+ and Mn2+.
Typical reactions of soap with water(CaCl2 and MgCl2 ) does not produce lather but for insoluble white scum or precipitate
2C17H35COONa + CaCl2 ? (C17H35COO)2Ca? + 2NaCl
2C17H35COONa + MgCl2 ? (C17H35COO)2Mg? + 2NaCl
There are basically two types of hardness:
1)Temporary hardness:
• Presence of dissolved bicarbonates of calcium and magnesium and other heavy metals • Removed by mere boiling • Carbonate hardness or alkaline hardness.
2) Permanent hardness:
Presence of dissolved chlorides and sulfates of calcium and magnesium, iron and other heavy metals • Not removed by boiling • Non-Carbonate hardness or non-alkaline hardness.
Degree of hardness:
Hardness of water is conveniently expressed in terms of equivalent amount of CaCO3.
CaCO3 Equivalent = (Amount of hardness producing substance)/(Equivalent weight of hardness producing substance)*(Equivalent weight of CaCO3)
Determination of Hardness:
• By complexometric titration
• Permanent hardness is usually determined by titrating it with a standard solution of EDTA by using Eriochrome Black-T
• The EDTA is a complexing, or chelating agent used to capture the metal ions
• This causes the water to become softened, but the metal ions are not removed from the water
Hardness removal methods:
1) By permutit process.
2) By ion exchange process.
3) By cold lime soda process.
4) By hot lime soda process.
Hardness rating Concentration of Calcium Carbonate (mg/L) Soft 0-50 Moderately soft 50-100 Slightly hard 100-150 Moderately hard 150-200 Hard 200-300 Very hard Greater than 300