Molarity of concentrated nitric acid = 15.9 M
Volume of the stock solution to be prepared = 500.0 mL
Concentration of the stock that is to be prepared = 0.750 M
Calculating moles from molarity and volume of stock:

Calculating volume of concentrated nitric acid to be taken for the preparation of stock solution:

Converting L to mL:
= 23.6 mL
Volume of distilled water to be added to 23.6 mL of 15.9 M nitric acid to get the given concentration = 5000.0mL-23.6mL=976.4 mL
Therefore, 976.4 mL distilled water is to be added to 23.6 mL of 15.9 M nitric acid solution to prepare 500.0 mL of 0.750M nitric acid.
Answer: 0.25M
Explanation: Because of the highest concentration of water and, if they are all the same volume, the greatest amount of water assuming it is a solid solute in a water solution.
Answer:
The frequencies of the two lines are:
a) 
b)
When we heat rubidium compound we will see red color.
Explanation:

c = speed of light
= wavelength of light
a) Frequency of the light when wavelength is equal to 



This frequency corresponds to red light
b) Frequency of the light when wavelength is equal to 



This frequency corresponds to violet light
When we heat rubidium compound we will see red color.
The answer is ( The concentrations of the products and reactants do not change.)