Table 3 Data for a Beer's Law plot
S1 (blank) S2 S3 S4 S5 S6
flask number
volume of NaSCN in
$1.0 \times 10^{-1} M$ $HNO_3$ solution
in standard solution, mL
0.00 2.00 4.00 6.00 8.00 10.00
final volume of standard
solution, mL
100.00 100.00 100.00 100.00 100.00 100.00
$SCN^-$ ion concentration in
standard solution, mol $L^{-1}$
0.00 $4.00 \times 10^{-5}$ $1.20 \times 10^{-4}$ $2.00 \times 10^{-4}$
$FeNCS^{2+}$ ion concentration
in standard solution, mol $L^{-1}$
0.00 $4.00 \times 10^{-5}$ $1.20 \times 10^{-4}$ $2.00 \times 10^{-4}$
%T of standard solution, % 100.00 80.2 65.8 53.0 45.4 38.6
absorbance of standard solution 0.000 0.0958 0.276 0.413
Table 4 Composition of equilibrium mixtures E1-E4
flask
number
E1 (blank)
E2
E3
E4
volume of
$2.00 \times 10^{-3} M$
$Fe(NO_3)_3$ in $1.0 \times 10^{-1} M$
$HNO_3$ solution, mL
50.00
50.00
50.00
50.00
volume of
$2.00 \times 10^{-3} M$
NaSCN in $1.0 \times 10^{-1} M$
$HNO_3$ solution, mL
0.00
10.00
30.00
50.00
total solution
volume, mL
100.00
100.00
100.00
100.00
Table 5 Analyzing the data
flask number
E2 E3 E4
initial $Fe^{3+}$ ion concentration, mol $L^{-1}$ $1.00 \times 10^{-3}$ $1.00 \times 10^{-3}$ $1.00 \times 10^{-3}$
initial $SCN^-$ ion concentration, mol $L^{-1}$ $2.00 \times 10^{-4}$ $6.00 \times 10^{-4}$ $1.00 \times 10^{-3}$
%T of equilibrium mixture, % 72.9 43.2 32.5
absorbance of equilibrium mixture 0.137 0.364 0.488
final equilibrium $FeNCS^{2+}$ ion concentration, mol $L^{-1}$ $1.35 \times 10^{-4}$ $2.83 \times 10^{-4}$ $3.37 \times 10^{-4}$
final equilibrium $Fe^{3+}$ ion concentration, mol $L^{-1}$ $8.65 \times 10^{-4}$ $7.17 \times 10^{-4}$ $6.63 \times 10^{-4}$
final equilibrium $SCN^-$ ion concentration, mol $L^{-1}$ $6.50 \times 10^{-5}$ $3.17 \times 10^{-4}$ $6.63 \times 10^{-4}$
equilibrium constant, $K_{eq}$ $2.40 \times 10^{3}$ $1.24 \times 10^{3}$ $7.67 \times 10^{2}$
mean $K_{eq}$ $1.47 \times 10^{3}$
