Question

Make sure that on your data table appears the correct number of significant figures! Solution Blank (diH2O) Absorbance y 0 Concentration (grams/mL) X 0 0.3708 0.185 Stock Diluted Solution #1 0.595 A 0.303A 0.150 A 0.074 Diluted Solution #2 Diluted Solution #3 Unknown 0.093 0.047 To be determined using Calibration Graph 0.68A Plot 2 Calibration Graphs 1) Use graph paper (on page 26) to create a calibration graph by hand. (Instructions are on page 27.) 2) Use MS Excel or the Graphical Analysis program. (Instructions start on page 29). Attach this graph to the back of your lab report. For each calibration graph, ✓ Plot Absorbance vs. Concentration (g/ml) using the five data points: (Blank, Stock, Solutions 1, 2, and 3) Absorbance is on y-axis and Concentration (g/mL) is on X-axis. Label each axis on the graph. Include where appropriate. ✓ Write a title above the graph. Example: "Absorbance vs. Concentration (g/mL) of_ " name the compound that was used in the experiment). Draw the "best fit" line. Do NOT connect the dots!!!

Create a calibration graph

Answer 1

A calibration curve can be plotted using MS excel or graph paper taking the gap of 0.1 on x-axis and y - axis

X axis = Concentration (g/ml ) , Y axis = Absorbance

Since the absorbance of unknown is lying out of the range ( even higher than stock) graph is extrapolated and value of the unknown is calculated by that.

0.684 unknown Absorbance ------- -- -- - conknown = 0.42 glad ou 0.5 0.6 0.2 o 0.1 0.2 0.3 concentration (g/ml)

I B I F G H J K L M C Conc (g/ml) D Absorbance known Absorbance vs Concentration 0.3708 0.185 0.093 0.047 0.595 0.303 0.15 0.071 0.595 Concentration Absorbance 0.424532352 0.684 Unknown 0.303 Absorbance 0.15 0.071 0 0.05 0.1 0.3 0.35 0.4 0.15 0.2 0.25 Concentration (g/ml)
Unknown Concentration in MS excel is calculated using formula =TREND(C2:C6,D2:D6,D9)

where C2 to C6 column contain concentration value and D2 to D6 column contain absorbance valve and D9 contain the absorbance of unknown. Now using the trend it can calculate the value of Concentration of unknown .

Concentration of unknown = 0.424 g/ml