[steuwotm8]

Hey there,

I require help on a few questions from the image below.



So my questions are:
- Why is the 'Concentration of final solution in linear region' is 18.0?
- How was the slope and intercept of the linear region calculated?
- How can the concentration be determined yes or no in accordance to the absorbance.
- How is 'Concentrated Pb' calculated if yes?

If you can't tell already, Chemistry is not my strongest in university and so I require help.

Please help me if you can. Detailed calculations and elaborations of my questions are required because chances are, I will not understand it fully.

Thank you!

[Hunter2]

This is done by mathematics of linear regression not region. A equation of y = m*x+b is developed with the datas. y = c(Pb), x = absorbance, m = slope and b = intercept.

The 18 ppm I think is obtained by calculating the sample.

y = 0.05851x -0.00224

[Arkcon]

Hey there,

So my questions are:
- Why is the 'Concentration of final solution in linear region' is 18.0?

I don't know what this problem, as written, means in this context.  I guess it means at least one analyzed sample was at that point.   Seems like a silly thing to mention, given there are 3 samples.

- How was the slope and intercept of the linear region calculated?

As was mentioned, linear regression is the formula used to draw the best (for varying definitions of the word) line through observed points.  If you had only two points, and two points define a line, slope would be determined by Δy/Δx, right?

- How can the concentration be determined yes or no in accordance to the absorbance.

Now this is an important topic to learn.  You can start by graphing this data, spreadsheet programs can do this for you.  I would look at the data points, the line defined by the formula given, and the r² value.  And see if you can guess what sort of data wouldn't fit.

- How is 'Concentrated Pb' calculated if yes?

Don't know what you're asking here.  You probably mean how to determine the concentration of an unknown from an observed absorbance.  You could use the graph to do it, but I hope once you build a graph, and label each axis, you'll be able to calculate backwards.  Try to consider: what is x, what is y, and if y=mx+b, how can you use that.

If you can't tell already, Chemistry is not my strongest in university and so I require help.

Please help me if you can. Detailed calculations and elaborations of my questions are required because chances are, I will not understand it fully.

Thank you!

We're glad to help, steuwotm8:, and welcome you to the Chemical Forums, but I'd like to ask you to read the Forum Rules{click}, we like to see a little more effort from you along with our help.

[Arkcon]

Note: after typing the data into a spreadsheet, I do see what this problem means by "Concentration of final solution in linear region' is 18.0," so if you try it as well, you should see why, and it will help you better understand the questions this problem is asking of you.