REGRESI LINEAR DENGAN LEAST SQUARES LINE

No X Y X2 Y2 XY1 0 0 0 0 02 5 0.12 25 0.0144 0.63 10 0.2 100 0.04 24 15 0.29 225 0.0841 4.355 20 0.42 400 0.1764 8.4

Jumlah 50 1.03 750 0.3149 15.35Rata 10 0.206

Sampel 0.35

Sxx=∑ x2−(∑ x )n

2

= 750 – 50x50/5 = 250

Syy=∑ y2−(∑ y )n

2

= 0.3149 – 1.03x1.03/5 = 0.10272

Sxy=∑ xy−∑ x∑ y

n = 15.35 – 50x1.03/5 = 5.05

β=SxySxx

=5.05/250 =0.0202

α= y−β x = 0.206 – 0.0202x10 = 0.004

Persamaan regresinya =

Y = 0.0202 X + 0.004

[Sampel] = (0.35 – 0.004)/0.0202 = 17.12871 ppm

Buatlah kurva kalibrasi untuk data yang lain.

1. A 6.81 grams pesticide sample was decomposed by wet ashing and then diluted to 200 mL in a volumetric flask. The analysis was completed by treating aliquots of this solution as indicated.

Volume of sample Taken, mL

Reagent volumes used, mLAbsorbance,

545 nm, 1 cm cell3.00 ppm Cu(II) Ligand H2O

50.0 0.00 20 30.0 0.37650.0 4.00 20 26.0 0.697

Calculate the percentage of copper in the sample.

2. A simultaneous determination for cobalt and nickel can be based upon absorption by their respective 8-hydroxyquinolinol complexes. Molar absorptivities corresponding to their absorption maxima are

Molar Absorptivity ε, at365 nm 700 nm

Co 3529 428.9Ni 3228 10.2

Calculate the molar concentration of nickel and cobalt in each of the following solution based upon accompanying data:

Solution Absorbance, A (1-cm cells)365 nm 700 nm

A 0.602 0.044B 0.650 0.040C 0.796 0.027

3. The acid-base indicator HIn undergoes the following reaction in dilute aqueous solution:

HIn H+ + In-

color 1 color 2The following absorbance data were obtained for a 5.00 x 10-4 M solution of HIn in 0.1 M NaOH and 0.1 M HCl. Measurements were made at a wavelength 485 nm and 625 nm with 1.00-cm cells.0.1 M NaOH A485 = 0.052 A625 = 0.8230.1 M HCl A485 = 0.454 A625 = 0.176In the NaOH solution, essentially all the indicator is present as In -; in the acidic solution, it is essentially all in the form of HIn.Calculate molar absorptivities for In- and HIN at 485 nm and 625 nm.Calculate the acid dissociation constant for the indicator if a pH 5.00 buffer containing a small amount of the indicator exhibits an absorbance of 0.472 at 485 nm and 0.351 at 625 nm (1-cm cells)