CHM256 (AS120) - Determination of Water Hardness Through EDTA Titration

[00:00:18]What is volutric analysis? Volutric analysis is a widely used quantitative analytical method. It is used to determine the concentration of an unknown solution by measuring the volume of a solution with a known concentration. This method is also known as titration. It works by measuring the volume of a second substance that reacts with the analyte in known proportions.

[00:00:41]The first volutric analysis method was developed by Jean Batista Andre Dummer.

[00:00:46]He used it to determine the amount of nitrogen present in organic compounds.

[00:00:51]Moving on to the different types of volutric analysis. There are four main methods we use in chemistry. Acid base, precipitation, complex symmetric and redux titrations for our topic force directly under complex titration which is a specific method used to bind and measure the metal ions responsible for water hardness.

[00:01:12]What is complexometric? Complexometric titration serve as a fundamental analytical method for examining one ratio one metalan reactions in aquis media specifically through the use of ethylene diamine tetra acidic acid EDTA to bind metal ions such as copper calcium and magnesium. The technique remains a highly reliable approach for determining milligram amounts of calcium in commercial mineral waters relying on classical indicators like calcium to deliver a sharp color transition at the end point. Imagine water flowing through limestone or dolomite rocks. As it travels, it picks up tiny minerals which are calcium and magnesium ions. The more of these ions it collects, the harder the water becomes. In fact, scientists like Indian and colleagues describe hardness simply as the sum of calcium and magnesium in water. And between the two, calcium usually plays the bigger role because it precipitates more quickly when heated. Now, why should we care? Think about your kettle or shower head. Hard water leaves behind chalky deposits that clogs pipes and even makes soap less effective. On the other hand, very soft water can be too aggressive that will corrode pipes instead. So, hardness isn't just chemistry. It is something we see in everyday life. But hardness isn't all bad. Calcium and magnesium are essential minerals for our bones and muscles. Drinking water gives us a small part of our daily intake.

[00:02:39]Still, studies show that very soft water may be linked to heart and bone health problems. So in a way, water hardness is both a nuisance and a necessity. There are two kinds of hardness. Temporary hardness comes from bicarbonates which you can remove it just by boiling water.

[00:02:56]Secondly, permanent hardness comes from sulfates and chlorides. And this time boiling won't help. To make it clearer, here's a skill. Soft water is below 60 mg per liter, while anything above 180 mg per liter is considered very hard.

[00:03:12]That's why we use charts like the one from Phily.com to visualize these ranges. So, how do we measure hardness?

[00:03:20]The standard laboratory method is complexometric titration with EDTA. This chemical binds both calcium and magnesium ions giving us a reliable measure of total hardness. Moving on to our methodology. Let's look at the material required for this experiment.

[00:03:36]We have categorized our setup into the three main section which is apparus, the chemical involved and the water sample itself. First for the apparatus we'll be using a 300 ml conical or lemon flask which will hold our water sample during titration. A 50 ml bureet to precisely dribble our titrate. A graduate pipet or measuring cylinder for volume measurement along with a standard beaker and a funnel to fill the burate safely.

[00:04:04]We also have dist water on hand for rising our glasses to ensure absolute cleanliness. Next looking at our chemical we will use a buffer solution calibrate to PH11 to maintain necessary alkine condition. Our condicator of choice is eurochrome black tea commonly known as the EV. And finally our titrate is a standard EDP solution. As for the water simple itself we are testing 50 ml of the tap water to ensure accuracy.

[00:04:34]This was collected in a truly clean container beforehand to completely avoid any external contamination.

[00:04:40]Now let's dive into the stepbystep procedure for the copymetric titration to determine the hardness of our water sample. So for the first one is the sample is been test is standard tap water collected directly for a manice time. Collect the tap water into a clean or pre- rice press be litter so that to ensure the collection container is completely free for uh any resident or mineral deposit to prevent cross combination of calcium and magnesium ion. Next let the water sit for a brief moment to ensure no air bubble are trapped which could interfere with volutric measurement. Also as you can see the the procedure set up is we have a magnetic steer of eliminated plus with a steer and also the bureete. First risk the clean bureet with a small amount of the EDTA solution to remove any residual distill that might dilute the nutrition.

[00:05:36]Then use a funnel to fill the bureate with the EDS solution until the miniscus right slightly past the zero mark. Open the stop pot completely for every second to flush out any air bubble trap in the bottom tip. Then carefully align the liquid level to the excess 0 ml starting line. Using a volutric pipe, make sure exactly 50 ml of the coated top water temple and transfer it into a clean 300 ml aluminial fl. Drop a magnetic steer into the flask. Add one to two drop of the imity indicator solution to the ps.

[00:06:08]Upon M6, the solution will immediately turn a distinct white, red or purple color indicating the present of the metal ion. Add exactly 10 ml of the PH11 bubble solution into the fast to establish and lock in the required alkan environment for the reaction. And the next one is place the aluminum flask into the magnetic steer space and turn on the motor to get a steady smooth vortex going. For the next one, position the flask under the burect tip and begin adding the EDS solution dropwise into the sample. Wash the color carefully.

[00:06:41]Stop the flow of the ENA titrate the exact moment the color change completely from one red to a stable clear blue.

[00:06:48]This size is show that the titration is at the end point. Read the gradation part on the bureet at the eye level and record the final volume of the EDTA consumed. So as you can see in the video the first R record is the 2.6 ml. Repeat this entire calculation process for a five more time which is six in the total to ensure position and account from any human error or from the video above. So it show an example of calculate the average volume of EDA consumed from all the social boost run. For the example of result we are analyzing a study published by applied food research in 2024. This graph tracks what happened to calcium and magnesium ions before and after boiling for 30 minutes. Let's focus on a clear example. Berlin tap water. Before boiling, the water is packed with both dissolved calcium and magnesium. However, look at what happened after 30 minute boil. The calcium drops significantly because it forms solid lime scale. And look at the magnesium bars. It stays exactly the same height. This mean short-term boiling has virtually zero effect on magnesium and it completely refuses to precipitate. So we use a volutric EDA titration and watch for a distinct color transition using an EBT indicator. When we titrate our initial unboiled tap water, the indicator binds with the free mineral to turn the solution wine red.

[00:08:11]Because both calcium and magnesium are fully present, it requires a large volume of EDTA from our bat to force the indicator to change color.

[00:08:19]However, when we titrate the water after it has been boiled and filtered, a huge portion of calcium has precipitated out.

[00:08:27]The EDTA quickly binds the remaining ions. So, the solution moves from purple to sky blue endpoint much faster. Since the study graph proved to us that the magnesium concentration never changed, it shows that the boiling process successfully soften the water by selectively removing the calcium.

[00:08:45]In conclusion, our presentation highlights compactometric titration using standard EDTA as a highly reliable quantitative method for determining water hardness specifically by measuring the total concentration of calcium and magnesium ions. By utilizing an aerocchrome lat indicator under stable conditions at BH10, the precise endpoint of the reaction is clearly signaled by a sharp color transition from white red to blue. Understanding and calculating these values is essential as managing water hardness not only prevents severe industrial and domestic engineering issues such as scale buildup and equipment corrosion but also directly impacts public health due to the vital role these minerals play in our daily biological functions.