Instrumental Analysis Lab Practical 1 Questions
with verified answers
Based on relative sensitivity and molar absorptivity, how can you tell
which instrument is more sensitive? Ans✓✓✓ Relative sensitivity,
instrument on denominator is more sensitive if the percent relative
sensitivity is <100%
The higher the molar absorptivity the more sensitive.
If one instrument has a larger molar absorptivity, but shows as less
sensitive to %Rel. Sens.
Take out the last two absorbance measurements and recalculate the
values because one may lose linearity towards the higher
concentrations, therefore the instrument with higher sensitivity here
would be more sensitive at lower concentrations.
Block diagram of spectrophotometers Ans✓✓✓ Light Source
Entrance Slit - beginning of monochromator
Grating
Exit Slit - end of monochromator
Sample
Detector
Read Out
, How do you calculate % Error? Ans✓✓✓ |Expected - Measured| /
Expected x100%
Significant Figures depends on the denominator (expected volume of
the pipettor)
How do you calculate Standard Error of the Mean? Ans✓✓✓ SD /
Square root of n
Find the first non-zero digit and that is you precision.
Example 0.00095480 mL = 0.00095 mL
How do you calculate the % Coefficient of Variance? Ans✓✓✓
SD/mean x100%
Percents only go to the hundredths place.
How do you calculate the concentration in a standard calibration tube?
Ans✓✓✓ Set up proportions.
Concentration of the known tube in g/dL divided by the unknown
concentration of the tube of interest = volume of diluted standard in
the known tube divided by volume of diluted standard in the tube of
interest.
with verified answers
Based on relative sensitivity and molar absorptivity, how can you tell
which instrument is more sensitive? Ans✓✓✓ Relative sensitivity,
instrument on denominator is more sensitive if the percent relative
sensitivity is <100%
The higher the molar absorptivity the more sensitive.
If one instrument has a larger molar absorptivity, but shows as less
sensitive to %Rel. Sens.
Take out the last two absorbance measurements and recalculate the
values because one may lose linearity towards the higher
concentrations, therefore the instrument with higher sensitivity here
would be more sensitive at lower concentrations.
Block diagram of spectrophotometers Ans✓✓✓ Light Source
Entrance Slit - beginning of monochromator
Grating
Exit Slit - end of monochromator
Sample
Detector
Read Out
, How do you calculate % Error? Ans✓✓✓ |Expected - Measured| /
Expected x100%
Significant Figures depends on the denominator (expected volume of
the pipettor)
How do you calculate Standard Error of the Mean? Ans✓✓✓ SD /
Square root of n
Find the first non-zero digit and that is you precision.
Example 0.00095480 mL = 0.00095 mL
How do you calculate the % Coefficient of Variance? Ans✓✓✓
SD/mean x100%
Percents only go to the hundredths place.
How do you calculate the concentration in a standard calibration tube?
Ans✓✓✓ Set up proportions.
Concentration of the known tube in g/dL divided by the unknown
concentration of the tube of interest = volume of diluted standard in
the known tube divided by volume of diluted standard in the tube of
interest.
