Explanation:
Pure subsance is a substance that is made up of only one type of particle - each piece is the same throughout.
Being present before the reaction but not after means it's no the same (it couldve evaporated)
Answer:
gram atomic mass
Explanation:
Mass of an atom expressed in grams is known as gram atomic mass. It is equal to the relative atomic mass or atomic weight in grams.
They are directly proportional to each other, in other words, when temperature of an object increases, the motion of it's particles also increases
Hope this helps!
Answer:
4
Explanation:
Relationship between wavenumber and Rydberg constant (R) is as follows:

Here, Z is atomic number.
R=109677 cm^-1
Wavenumber is related with wavelength as follows:
wavenumber = 1/wavelength
wavelength = 253.4 nm

Z fro Be = 4

Therefore, the principal quantum number corresponding to the given emission is 4.