Question

I'm a 14-year-old student embarking on my first chemistry assignment. My teacher has tasked me with conducting a chloride titration of drinking water. There's just one condition: I must avoid using any hazardous substances. I've scoured the internet, but I've found only a limited number of reports. Could someone please assist me with this challenge?

Answer 1

Chloride titration can be performed using sodium thiosulfate and starch as an indicator while avoiding hazardous substances. By adding potassium iodide to chlorinated water and titrating with sodium thiosulfate, the chlorine content can be measured safely.

Step-by-step explanation:

The chloride titration of drinking water is an essential exercise in analytical chemistry to quantify the amount of chlorine present in water.

To conduct a chloride titration without using hazardous substances, one can follow a method similar to the one described in Standard Methods for the Examination of Water and Wastewater. This method involves acidifying the water sample with glacial acetic acid, adding potassium iodide (KI), and then titrating with sodium thiosulfate (Na2S2O3) using starch as an indicator.

When chlorinated water is chemically reactive with KI, it produces iodine which can be quantified by titrating with sodium thiosulfate. The endpoint of the titration is noted when the blue color from the starch-iodine complex disappears. It's crucial to perform a blank titration to correct for any impurities in the reagents used. This method is aligned with avoiding hazardous chemicals as none of the reagents mentioned pose significant risk under proper use.