Chemistry

You are measuring a number of samples taken from a field where copper sulphate contamination is suspected. Answer the following questions to proceed with this investigation

First you would have to make up a stock solution What weight of copper sulphate would you need to make a 0.8M copper sulphate solution in a 500ml volumetric flask

To prepare a 500mL stock solution of 0.8M copper sulphate, weigh 63.84g anhydrous CuSO4, dissolve in enough amount of distilled water. Transfer solution to a 500mL and fill with distilled water up to mark and mix well.

Next you would make up the standards  How much stock solution would you have to put into 100ml volumetric flasks to make up the following solutions

Standard concentrationAmount of stock standard needed (mL)0.70087.500.60075.000.50062.500.40050.000.35043.750.20025.000.15018.750.0506.250.0020.25
 
You run the standards through a spectrophotometer to get a calibration curve.  You get the following results

Standard ConcentrationSpectrophotometer reading0.7000.07200.6000.06600.5000.05000.4000.04600.3500.02900.2000.01600.1500.01000.0500.00700.0020.0003

From these results generate a calibration curve in Excel.  What is the R2 value

R2 value  0.976

Using the equation obtained from the calibration curve work out the copper sulphate concentrations for the following samples

Sample numberSpectrophotometer readingConcentration of Copper sulphate (M)Average Concentration10.0420.4110.374020.0400.39330.0350.34640.0500.48650.0230.23460.0560.5420.489870.0600.57980.0460.44990.0410.402100.0490.477

Samples 1-5 were taken from a field that contained normal environmental levels of copper sulphate.  Samples 6-10 came from a field where copper sulphate contamination is suspected.

In no more than 100 words state whether you think that samples 6-10 come from a field contaminated with copper sulphate. You may use an appropriate statistical analysis if you wish.

Based on the determined average concentrations of copper sulphate in the samples, it can be observed that samples 6-10 have relatively higher amounts than samples 1-5. However, to confirm if the samples 6-10 are indeed contaminated with copper sulphate it should be compared to the threshold levels of copper sulphate in the soil.