# Determining the concentration of ions in ppm

• Chemistry
• rwooduk
In summary, the paper describes a study on the formation of calcium carbonate scale in pipes and the effects of different conditions and additives. It mentions using a test solution with a final concentration of 3500 ppm Ca+2, which corresponds to a molarity of 0.0875M. The equimolar concentrations of sodium carbonate and calcium chloride were chosen to give this concentration of Ca+2 in the calcium chloride solution. This may cause some confusion as the wording could imply that the sodium carbonate solution was made from calcium chloride crystals, but it appears that the 3500 ppm Ca+2 concentration is for the mixed solution. However, it is not clear why this specific concentration was chosen and whether it is a dynamic steady-state value.
rwooduk
Homework Statement
It's in a paper I am reading (not homework)
Relevant Equations
ppm = (mass of solute ÷ mass of solution x 1,000,000
I'm a little confused by a basic statement in a paper I am reading. It says that calcium chloride (1 M) and sodium carbonate (1 M) i.e. equimolar, have "a predetermined concentration of 3500 ppm of Ca2+"...

I understand that the mixing of these two will cause a precipitation reaction, but don't understand how the ppm of calcium ions was determined, was it measured / calculated somehow? Why would there be Ca2+ in the sodium carbonate solution? The statement seems a little confusing.

Thank you in advance for any help understanding this.

EDIT paper is Calcium carbonate scale formation in pipes: effect of flow rates, temperature, and malic acid as additives on the mass and morphology of the scale

It says they are equimolar; that is the molar concentrations of sodium carbonate and calcium chloride are equal to each other; they are not necessarily equal to 1M. 3500ppm Ca2+ is 0.0875M. There is no Ca in the sodium carbonate solution - there can't be; the statement must mean that the (equal) molar concentration was chosen to give 3500ppm Ca2+ in the calcium chloride solution. It is a little awkwardly expressed, I agree.

rwooduk
mjc123 said:
It says they are equimolar; that is the molar concentrations of sodium carbonate and calcium chloride are equal to each other; they are not necessarily equal to 1M. 3500ppm Ca2+ is 0.0875M. There is no Ca in the sodium carbonate solution - there can't be; the statement must mean that the (equal) molar concentration was chosen to give 3500ppm Ca2+ in the calcium chloride solution. It is a little awkwardly expressed, I agree.

Thank you mjc. So, then I guess that the ppm was calculated by using the mass of calcium chloride required to give 1 M solution divided by the mass of solution, would that be correct?

Also, it says...

So, that would be equimolar right?

rwooduk said:
So, then I guess that the ppm was calculated by using the mass of calcium chloride required to give 1 M solution divided by the mass of solution, would that be correct?
No. First, it is ppm of calcium, not calcium chloride. Second, I have already told you that 3500 ppm Ca corresponds to a molarity of 0.0875M, not 1M.
rwooduk said:
So, that would be equimolar right?
Yes. You didn't tell us this before. Is there any more information you're hiding? It's not clear to me now what's going on, or what the 3500ppm refers to. It can't be the stock solutions if they are 1M. Are the stock solutions diluted before being mixed? Your quote suggests not. Is 3500ppm the concentration of Ca2+ after mixing the solutions? I wouldn't have thought so; CaCO3 is not that soluble. I'm really confused now.

jim mcnamara
Apologies for the confusion and thank you for the further help with this. The paper is Calcium carbonate scale formation in pipes: effect of flow rates, temperature, and malic acid as additives on the mass and morphology of the scale

The excerpts from the paper which I uploaded as images are from Section 2.1.

https://www.sciencedirect.com/science/article/pii/S1876619614000102

Hmmm. It's still not quite clear. It looks like 3500 ppm is the concentration of Ca2+ in the mixed solution. The initial concentration would be 0.5M (20,000 ppm), and I would expect the concentration after complete precipitation to be lower than 3500, but this is a flow system, and deposition is slow, so maybe 3500 ppm is a dynamic steady-state value. They could have been clearer. (For example, the wording literally implies that the sodium carbonate solution was made from calcium chloride crystals!)

rwooduk
mjc123 said:
Hmmm. It's still not quite clear. It looks like 3500 ppm is the concentration of Ca2+ in the mixed solution. The initial concentration would be 0.5M (20,000 ppm), and I would expect the concentration after complete precipitation to be lower than 3500, but this is a flow system, and deposition is slow, so maybe 3500 ppm is a dynamic steady-state value. They could have been clearer. (For example, the wording literally implies that the sodium carbonate solution was made from calcium chloride crystals!)

Thanks mjc for taking the time to read the section of the paper. Yes, I was quite confused by their description. Your interpretation has been a great help. Thank you.

Actually, the paper merely states that the test solution was prepared from a stock 1M solution to a final concentration of 3500 ppm Ca+2. That would mean that the test solution would be at 7000 ppm Ca+2 and the CO3-2 solution would be at whatever ppm CO3-2 would be equimolar with that.

rwooduk

## 1. What is ppm?

PPM stands for parts per million, which is a unit of measurement used to express the concentration of a substance in a solution. It represents the number of parts of a solute per million parts of the solution.

## 2. Why is it important to determine the concentration of ions in ppm?

Determining the concentration of ions in ppm is important because it allows us to accurately assess the purity or contamination of a solution. It is also useful in determining the effectiveness of a particular treatment process or the concentration of a certain element in a sample.

## 3. How is the concentration of ions in ppm calculated?

The concentration of ions in ppm is calculated by dividing the mass of the solute by the total mass of the solution and then multiplying by 1,000,000. This value can also be obtained by multiplying the molarity of the solution by the atomic mass of the solute and then multiplying by 1,000,000.

## 4. What are some common methods for determining the concentration of ions in ppm?

There are several methods for determining the concentration of ions in ppm, including titration, spectrophotometry, and ion-selective electrodes. These methods involve measuring the amount of a substance present in a sample and using mathematical calculations to determine the concentration in ppm.

## 5. How can the accuracy of measuring ppm be ensured?

To ensure the accuracy of measuring ppm, it is important to use high-quality equipment and follow precise procedures. It is also important to calibrate equipment regularly and use multiple methods for confirmation. Additionally, proper handling and storage of samples can also affect the accuracy of the measurement.

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