Calculations :

Standard solution preparation

Standard 1:

M1V1 = M2V2

(300)(V1) = (5)(20) V1 = 0.333 mL

Standard 2:

M1V1 = M2V2

(300)(V1) = (20)(20) V2 = 1.333 mL

Standard 3:

M1V1 = M2V2

(300)(V1) = (40)(20) V1 = 2.667 mL

Standard 4:

M1V1 = M2V2

(300)(V1) = (60)(20) V1 = 4.000 mL

Standard 5:

M1V1 = M2V2

(300)(V1) = (80)(20) V1 = 5.333 mL

Standard 6:

M1V1 = M2V2

(300)(V1) = (100)(20) V1 = 6.667 mLBy plotting graph 1,gradient of the graph, m = y2 - y1

X2 - x1

= 0.034-0.011

80-20

= 0.0004 Abm/ppm

Hence, the equation of line is ;

Y=mx + cy = 0.0004x + 0.0035

To find the value of x, y = 0.058 Abm X = y - 0.0035 0.0004X = 0.058 - 0.0035 0.0004X = 136.25 ppm

Results

Table1 : Concentration of chromium(iv) solution and its absorbance

Concentration (ppm)

Volume (mL) Absorbance (abm)

Standard 1 5 0.33 0.001

Standard 2 20 1.33 0.011

Standard 3 40 2.67 0.014

Standard 4 60 4.00 0.026

Standard 5 80 5.33 0.034

Standard 6 100 6.67 0.043

Table2 : Types of water sample and its absorbance value

Water sample (lake) Absorbance value (abm)

Tasik Cheras (outlet) 0.014

Tasik Seksyen 7(100m from inlet)

0.031

Tasik Cheras (50m from inlet)0.058

Tasik Cheras (inlet)0.080

Tasik Seksyen 7 (50m from inlet)0.097

Tasik Seksyen 70.118

Graph 1shows the value of absorbance against concentration of chromium (iv) solution

y2 - y1

x2 - x1

Concentration of Crromium (IV) parts per million

Absorbance value

(abm)