Question

 

Assume you forgot to condition the 25.00 mL volumetric pipette after making each standard solution

a.) How would the incorrect standard solution concentrations affect the y-intercept of your calibration curve?

b.) How would the incorrect slope and y-intercept of your calibration curve affect the value of the molar absorptivity you measured for your dye?

c.) How would the incorrect molar absorptivity affect the absorbance measurement for your dye in the water enhancer solution?

d.) How would the incorrect absorbance measurement affect your calculated value for the concentration of your dye in the water enhancer solution?

Answer 1

a) The incorrect standard solution concentrations will give wrong or deviated values of absorbance (y-intercept ) for the Absorbance vs concentration callibration Curve.

According to Beer's law, Absorbance,A=elC ,where e=molar absorptivity of the chemical species,l=path length of light ,C=concentration of the species.

So Concentration is directly proportional to the Absorbance, thus if wrong value of concentration is taken ,the Absorbance will also be affected

C=C+C ,where C=error,

A=el(C+C)=elC +elC=A+A [the error is multiplied by absolute value of el ,the constant]

b)Slope for A vs C curve is el. where e=molar absorptivity,l=path length of light =constant

y-intrcept is Absorbance

So, error in slope directly affects e,with an error equal to S/l

for slope=S+S=el+e*l , where S=el

A=(e+e)*l(C+C)=A+A   where A=elc ,A=error in A=l(C+e) [rule of propagation of error for multiplication)

c)The callibration curve is used to find out the Absorbance of the given water enhancer solution of known concentration.Thus,Absorbance value for its known concentration C(known) is given by ,

A=(e+e)*l(C(known))=A+A  

where A=elc ,

A=error in A=C(known)*l*(e)

d)For unknown concentration, C(unknown )of dye in the water enhancer solution,

C(unk)=(A+A)/ el=A/el +A/el=C+C ,.error in C(known)=A/el