# Help with Calculating PPM of Chlorine

• Meron35
In summary, an investigation is being conducted on the quality of chlorinated pool water and the amount of free chlorine present. The water being tested is labeled as 200 ppm and is stabilized with an unknown amount of cyanuric acid. The experiment involved using methyl orange to determine the amount of free chlorine, with an average of 0.14mL of pool water being needed to turn the solution clear. However, when trying to calculate the ppm, a discrepancy of 775ppm was found. It is unclear why this is happening, but it is possible that the 200 ppm is referring to a different type of chlorine that is not bound with cyanuric acid. Further investigation is needed to determine the cause of this discrepancy.
Meron35
We are currently undertaking an investigation into chlorinated pool water and how various factors can affect the quality of it. We are attempting to determine the amount of "free chlorine" (HOCl/OCl-) in a given sample of pool water.
This pool water is labelled as 200 ppm, and is "stabilized" with an unknown amount of cyanuric acid. We do know that the water is chlorinated with sodium hypochlorite.

We have tried to determine the amount of free chlorine in solution by using methyl orange. Acidified methyl orange (red) reacts 1:1 with HOCl/OCl-, and turns clear. The experiment we conducted is as follows:
2.00mL of methyl orange (0.5g/L or 0.00153mol/L) was put in a reaction vessel
HCl was added until the solution turned red
Pool water was titrated into the solution until it turned clear

The experiment was repeated 3 times, and on average 0.14mL of pool water turned the solution clear.
However, when we try to use these results and find out what the ppm of pool water is, we keep getting around 775ppm, which seems way too high. We calculated it as followed (this method was given to us in an experimental booklet):
((concentration of methyl orange)*volume of methyl orange/volume of pool water)*35.5*1000

Is this sort of discrepancy normal? If so, why? If not, what and where could we have gone wrong and why?

Doesn't look normal, but the general idea and your calculations look reasonably correct.

Perhaps 200 ppm is a concentration of "free" chlorine, one that is not bind with cyanuric acid? But that's just a random guess, I know nothing about the pool chemistry.

## 1. What is PPM and why is it important in calculating chlorine levels?

PPM stands for parts per million and it is a unit of measurement used to express the concentration of a substance in a solution. In the context of calculating chlorine levels, PPM is important because it allows us to accurately measure and track the amount of chlorine present in a solution, such as a pool or drinking water.

## 2. How is PPM of chlorine calculated?

The PPM of chlorine is calculated by dividing the weight of chlorine in a solution by the weight of the solution, and then multiplying by one million. This calculation can be done using a scale to measure the weight of the solution and a test kit to measure the weight of the chlorine.

## 3. What is the acceptable PPM range for chlorine in a pool or drinking water?

The acceptable PPM range for chlorine in a pool is typically between 1-3 PPM. For drinking water, the recommended range is between 0.2-2 PPM. It is important to regularly test and maintain chlorine levels within these ranges to ensure the water is safe for use.

## 4. How does temperature affect PPM of chlorine?

Temperature can affect the PPM of chlorine in a solution. As temperature increases, the chemical reactions that involve chlorine also increase, resulting in a decrease in PPM. Conversely, as temperature decreases, the chemical reactions slow down, resulting in an increase in PPM. This is why it is important to regularly test and adjust chlorine levels in a pool or drinking water, especially in warmer temperatures.

## 5. Can PPM of chlorine be converted to other units of measurement?

Yes, PPM of chlorine can be converted to other units of concentration, such as milligrams per liter (mg/L) or milligrams per kilogram (mg/kg). These conversions can be done using conversion factors and are useful when comparing chlorine levels to regulatory standards or other sources of measurement.

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