Q 20.17: In IR spectroscopy, a conjugated ketone will produce a C=O signal at a wavenumber, compared with a non-conjugated ketone of similar structure.

See explanation

Explanation:

Infrared spectroscopy is concerned with transitions between vibrational energy levels. Each infrared active vibration leads to a change in dipole moment.

A ketone compound contains the -C=O group whose signal normally occurs at about 1710 cm-1.

A conjugated ketone is one in which the -C=O group is attached to the -C=C  group. This leads to delocalization and reduces the electron density of the C=O  double bond, which weakens this bond hence lowering the stretching frequency of the  -C=O bond from  1710 to about 1680cm-1.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.