Using Linear Equation to Solve for Chemical Concentration

[Shelby21]

Hi guys,

I need some help with coming up with an Excel formula to solve a linear equation for chemical concentration.

I think this one is a bit complex and not even sure if it is possible to create a formula since there are two equations and each equation relies on input from one another.

You are going to need your thinking cap


We start with the spreadsheet below where you need to input your flowrate for NH4OH and DIW in cells C69 and D69

Once you input NH4OH and DIW flow, the sheet looks like below:

The problem I am running into is that to solve for concentration, I need to know what the NH4OH loss due to evaporation is and to solve for NH4OH loss due to evaporation I need to know what the concentration is.

The statement above can be explained by the 2 equations shown below:

Currently, the only way I am able to calculate this is by looking at live data as shown below:

concentration is 9560 ppm
DIW flow is 10.16 L/min
NH4OH flow is 403 mL/min.

I am having to take the live concentration value in the chart above and plug into the NH4OH loss due to evaporation equation using symbolab to solve for x

Once, I get the x-value of 17.00, I have to manually plug this into my concentration equation which is shown above and is represented by cell C81


What I would like to do:

Be able to calculate the NH4OH loss due to evaporation and the concentration without the need for live data or using symbolab to solve linear equation.
I want to have everything setup as formulas within Excel so I can simulate flowrate changes and expected concentration based off the flow changes.

 

[shg]

If you know the concentration, can't you just use algebra to solve for x in that equation?

 

[Shelby21]

If you know the concentration, can't you just use algebra to solve for x in that equation?

shg,

Yes, but that's not the purpose of what I am trying to do.

In the last statement, where I stated what I would like to do:

Be able to calculate the NH4OH loss due to evaporation and the concentration without the need for live data or using symbolab to solve linear equation.
I want to have everything setup as formulas within Excel so I can simulate flowrate changes and expected concentration based off the flow changes.

What if I don't know the concentration or I am troubleshooting a concentration issue. I want to be able to input my flowrates and have the Excel sheet display what the concentration should be and then I can compare to live data to see if their is difference between expected vs actual concentration.

 

[shg]

Sorry, reckon I don't understand the problem.

If you stir some amount of ammonia into water, don't you know the initial concentration (before evaporation starts)?

Excel solves equations for a living.

 

[Shelby21]

Sorry, reckon I don't understand the problem.

If you stir some amount of ammonia into water, don't you know the initial concentration (before evaporation starts)?

Excel solves equations for a living.

sure, if you stir in the same amount of ammonia each time into the same amount of water. What happens when you add more or less ammonia or water the next time you mix them. Do you still know what the initial concentration should be?