STATICTICS FOR ANALYTICAL CHEMISTRY Essay Example
 Category:Chemistry
 Document type:Assignment
 Level:Masters
 Page:1
 Words:437
Equation for the variance of e
The variance e is the absorbance which largely depends on the concentration of the solution, a plotting a line of best fit will enable us to know the absorptivity of the solution
Therefore, Y= mx + c
Y in this equation is the absorbance whereas the x is the concentration
e=A.V/l.m
e=l.mx + A.V
x is the slope of the plotted graph
Equation 2
A =log_{10 }(l_{o}/l)
A=ln (I)In (I_{o})
=In (l/l_{o})
Standard Deviation of Absorbance (SD_{A})
As indicated in the curve above, the relative standard deviation of the absorbance is variable since the absorptivity increases as theconcentration of the solution increases.
Therefore, the optional choice of range should be increased abit so as to be able to deduce the most accurate absorptivity level in the solution
Q5 Determination of manganese in steels
1.18* (0.35/1.15)=0.359
1.17* (0.35/1.15)=0.356
1.21*(0.35/1.15)=0.368
1.19*(0.35/1.15)=0.362
Sample Absorbance Manganese(ww/Mn)
1 0.359 1.18
2 0.356 1.17
3 0.368 1.21
4 0.362 1.19
Slope=∆Y/∆X
Slope=(0.3590.356)/(1.181.17)
1.18=0.3(1.17) + C
C=0.829
Y= 0.3(0) 0.829
Y intercept=0.829
The concentration of manganese from the solution is equivalent to the absolute value of the xintercept
X intercept=(0.829/0.3)=2.7633
The manganese in the sample is equivalent 2.7633 ww/Mn
The contents in the solution 2.7633 *(0.35/1.15)= 0.8409 mg of Manganese in the sample
Therefore, both the lowest and highest estimated values falls within the range of the Manganese concentration.
tTest Statistics
t=[│r│√(n2)]/√(1r^{2})
t^{2}=r^{2}(n2)/(1r^{2})
t^{2}(1r^{2})=r^{2}(n2)
t^{2}t^{2}r^{2}=nr^{2}2r^{2}
nr^{2}2r^{2}+t^{2}r^{2}=t^{2}
r^{2}(n2+t^{2})=t^{2}
=t/(√(t^{2}+n2)
3 2.85 0.312

2.43 0.307

2.23 0.280

2.09 0.250

1.95 0.222

1.90 0.198

1.87 0.178

1.84 0.162
11 1.80 0.147
As indicated indicated in the graph above, there is significantyly linear correlation between the confidence level of the two variables hence the null hypothesis should be rejected
Determination of the concentrationof HCI in a solution
Indicator Mean HCI concentration(SD)/mol L^{1} Number of titration experiment
Bromothymol 0.09656(0.00023) 28
Methyl red 0.08686(0.00098) 18
SUMMARY OUTPUT 

Regression Statistics 

Multiple R 

Adjusted R Square 

Standard Error 
0 

Observations 

Significance F 

Regression 

Residual 
0 
0 

Coefficients 
Standard Error 
Lower 95% 
Upper 95% 
Lower 90.0% 
Upper 90.0% 

Intercept 
0 

X Variable 1 
0 


In relation to the summary output above, the the standard deviation of the two variables do not significantly differ from each other since they are positively correlated with a correlation coeffiecient of 0.0694

The difference between Indicator 1 and Indicator 2 is insignificant based on the fact that the significant F is zero and the Lower and upper limit of confidence level 90% is 0.0694
Q12 The Absorbance,A of a solution A= log_{10} (T) where T is the transmittance
A= log_{10} (T)
=0.501 +0.001
A=log_{10}(0.502)
A=(0.2993)
A=0.2993
Absorbance 0.299
Standard deviation 0.0003