Just to make sure I’m right, is number 1 miss spelled??
<u>Answer:</u> The energy of one photon of the given light is 
<u>Explanation:</u>
To calculate the energy of one photon, we use Planck's equation, which is:

where,
= wavelength of light =
(Conversion factor:
)
h = Planck's constant = 
c = speed of light = 
Putting values in above equation, we get:

Hence, the energy of one photon of the given light is 
The moles can be defined as the mass of the substance with respect to molar mass. The moles of potassium nitrate is 1 mol.
<h3>How to calculate moles of a substance?</h3>
The moles of a compound can be calculated from:

The molarity can be defined as the moles of solute in a liter of solution.
The molarity can be expressed as:

The molarity of potassium nitrate solution is 2 M, and the volume is 500 mL.
The moles of potassium nitrate is given as:

The moles of potassium nitrate in 2 M, 500 mL solution are 1 mol.
Learn more about moles, here:
brainly.com/question/15209553
The answer is Rubidium (Rb)
The equation is balanced as follows
Mgcl2 +2AgNo3 -->2Agcl +Mg(No3)2
from equation above 1 mole of MgCl2 reacted with 2 moles of AgNo3 to form 2 moles of AgCl2 and 1 mole of Mg(NO3)2
when balancing equation the number of atom of element should be the same on each side of equation.