Chapter 3

Question 1

Define spectrophotometer

Answer 1

Molecular spectroscopy based upon the UV - visible radiation is used for identification and quantification of inorganic, organic and bio medical species

Question 2

(Quantitative analysis) Spectrophotometer is probably more widely used in…

Answer 2

Chemical and clinical laboratories

Question 3

Spectrophotometer for qualitative analysis is used in…

Answer 3

Research laboratories

Question 4

Define quantitative analysis

Answer 4

Using UV/ vis spectroscopy to analyze a sample to know the analyte concentration

Question 5

Quantitative analysis methods

Answer 5

1- Calibration curve
2 - standard addition (complex sample)
3- internal standard (compensate for randomand systemic errors: difficult.

Question 6

……. Is used mainly in chromatography

Answer 6

Internal standard

Question 7

Blank contains……

Answer 7

All substrates/ reagents except the analyte

Question 8

Blank in single beam instrument is used to set the absorbance to…….

Answer 8

Zero

Question 9

Setting the absorbance to zero…..

Answer 9

Removes and absorption of light due to these substances and the cell. Thus making the measured absorbance representative to the analyte only

Question 10

( calibration curve ) Beers law is used for…….

Answer 10

Quantitative analysis of the sample solution by measuring the absorbency at a wavelength at which analyte in the solution is having maximum absorption.

Question 11

A is stand for

Answer 11

absorbance and it have no unit

Question 12

٤ stand for

Answer 12

Molar absobivity

Question 13

Define single point calibration

Answer 13

Measuring the absorbance of a standard solution of the analyte and them seasure the absorbance of the unknown solution of the anylate

Question 14

C (concentrain) have a unit…..n

Answer 14

U (micro) g /ml

Question 15

An unknown solution had an absorbance of 0.592 at a wavelength of 625nm. A standard solution with a
concentration of 250 µg/ml had an absorbance of 0.308 at the same wavelength and under the same conditions .What is the concentration of the unknown solution ?

Answer 15

A ( unk ) = 0.592
C (ST)= 250 ug/ml
A (ST)= 0.308
C (unk)=?

C (unk)= A (unk) x c (ST)/ A (ST)= 480.51 ug/ml

Question 16

Many non absorbing analytes can be determined spectrometrically…….

Answer 16

By causing them to react with chromophoric reagents to give products that absorb strongly in the uv-visible regions

Question 17

Inorganic reagents

Answer 17

Thiocyanate ion for iron, cobalt and molybdenum.
Iodide ion for bismuth, palladium etc.

Question 18

Organic chelating reagents

Answer 18

Form stable colored complex with cations

Diphenylthiocarbazone for lead
1,10 - phenanthroline for iron
Dimethylglyoxime for nickel

Question 19

Alcohols can be estimated by

Answer 19

Formation of red Color 1:1 complexes formed between aliphatic alcohol and cerium ( IV )

Question 20

The amount of iron present in a sample is determined by

Answer 20

Reacting the iron with 1,10- phenanthrolineto form a red colored complex

Question 21

Calibration curve neg

Answer 21

Conclusions based upon a single measurement are not statistically sound, because it is easy to make measurement but difficult to measure the errors

Question 22

Standard addition method usually involves….

Answer 22

Adding known amount of standard solution to sample aliquots of the same size

Question 23

We can’t use calibration curve with…….

Answer 23

Unclean sample

Question 24

X-axis curve represent….

Answer 24

the volume of standard solution which Has the same amount of update an the unknown

Question 25

Spectrophotometric titration is used when

Answer 25

If the analyte, the titrant or the reaction product any one absorbs radiation in the UV- visible regions, absorbency measurement a fixed wave length can be used to locate the end point of the titration,