Question

LabQuest DATA TABLE xoomum Abs.097 Trial Concentration (M) .080 Absorbance h .19 L2 .223 .24 .32 6350 0474 .40 Unknown .589 .409 DATA ANALYSIS 1. Using Excel create a calibration curve from your data. Include the chart with your results section. a. Provide the line equation for your standard curve: b. Provide your obtained correlation coefficient: 2. Provide your calculated unknown concentration:

Answer 1

1.

The data of absorbance and concentration is

В Concentration(M) Absorbance 1 2 0.08 0.119 3 0.16 0.223 0.24 4 0.35 5 0.32 0.474 6 0.4 0.589

Now, plotting absorbance in y axis and concentration in x axis, we get the following straight line fitted graph:

Absorbance vs Concentration 0.7 y 1.4888x-0.0063 0.6 R2 0.9991 0.5 0.4 0.3 0.2 0.1 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 Concentration (M) Absorbance

a.

From the graph, the equation of the standard curve is

Where

y = Absorbance

x = concentration in M unit

b.

Correlation coefficient of the plot is 0.9995, calculated using the CORREL(A2:A6, B2:B6) function in excel.

It suggests a direct linear relationship between absorbance and concentration.

2.

Unknown has an absorbance value of 0.409

Hence, putting y = 0.409 in the standard fit equation, we can calculate x which corresponds to the unknown concentration

Hence,

$y = 1.4888 x - 0.0063 \\ \Rightarrow 0.409 = 1.4888 x - 0.0063 \\ \Rightarrow x = \frac{0.409+0.0063}{1.4888} \approx 0.279 \ M \approx {\color{Red} 0.28 \ M}$

Hence, the unknown concentration is 0.28 M approximately.