The appropriate value in blank given is Δf = 5.5 x  Hertz.
 Hertz.
We have vibrational - rotational spectrum Hydrochloric Acid.
We have to investigate the estimated separation between absorption peaks and fill the blank.
<h3>What is vibrational - rotational spectrum ?</h3>
Rotational–vibrational spectroscopy is a branch of molecular spectroscopy. It deals with the infrared and Raman spectra of molecules in the gaseous phase.
According to the question -
The estimated separation between absorption peaks in the vibrational-rotational spectrum of HCl is denoted by Δf and is equal to -
Δf = 5.5 x  Hertz
 Hertz
Hence, the appropriate value in blank given is Δf = 5.5 x  Hertz.
 Hertz.
To learn more about vibrational-rotational spectrum, visit the link below-
brainly.com/question/18403840
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<h2>
Answer: Infrared light</h2>
A dark nebula is a cloud of dust and cold gas, which does not emit visible light and hides the stars it contains.
These types of nebulae are composed mainly of the hydrogen they obtain from nearby stars, which is their fuel.
It is using infrared light that we can "observe" and analyze in detail what happens in the inner parts of these nebulae.
 
        
        
        
Valleys are one of the most common landforms on the Earth and they are formed through erosion or the gradual wearing down of the land by wind and water. In river valleys for example, the river acts as an erosional agent by grinding down the rock or soil and creating a valley
 
        
             
        
        
        
12.5 times 14 and convert to meters its 1.75 meters per second 
 
        
                    
             
        
        
        
Star 1 - 4 hours right ascension
 Star 2 - 3 hours right ascension
 Subtracting hours right ascension
 4 hours right ascension - 3 hours right ascension = 1 hours right ascension.
Thus,
 star 1 will rise 1 hour before star 2