<u>Answer:</u> The wavelength of spectral line is 656 nm
<u>Explanation:</u>
To calculate the wavelength of light, we use Rydberg's Equation:

Where,
= Wavelength of radiation
= Rydberg's Constant = 
= Final energy level = 2
= Initial energy level = 3
Putting the values in above equation, we get:

Converting this into nanometers, we use the conversion factor:

So, 
Hence, the wavelength of spectral line is 656 nm
Answer:
The same number of molecules, 6.0 × 10²³ molecules.
Explanation:
The amount of any given gas that can be stored in a container depends on the <u>temperature, pressure and volume </u>of the container. It does not depend on the nature (or identity) of the gas.
So if a 10-liter flask contains 6.0 × 10²³ molecules of hydrogen gas, it will contain the same amount of molecules of any other gas when temperature and pressure remain constant.
Hi the answer is actually B
I can't tell because I can't see the picture but it seems like