To calculate the pH of a solution that has a [H3O+] of 7.22x10^-7. You would do the following
pH=-log[H3O+]
pH=-log[7.22x10^-7]
pH=?
The 3d sublevel is not filled until after the 4s sublevel, because the 3d sublevel has more energy than the 4s sublevel, and less energy than the 4p sublevel. (:
Answer : The energy released by an electron in a mercury atom to produce a photon of this light must be, 
Explanation : Given,
Wavelength = 
conversion used : 
Formula used :
As, 
So, 
where,
= frequency
h = Planck's constant = 
= wavelength = 
c = speed of light = 
Now put all the given values in the above formula, we get:
Therefore, the energy released by an electron in a mercury atom to produce a photon of this light must be,
Is this a test or something else?
There are two kinds of analysis: qualitative and quantitative
In quantitative we analyse the amount of something that is how much of something is present / the quantity. Ex: the length of branch of tree, number of students in class, volume of a liquid in a beaker.
In qualitative analysis we determine the kind of substance / quality of substance / nature of substance.
like: colour of a substance, odor of a substance or taste (bitter / sour / sweet etc) of a substance
So answer is : B.The substance tastes bitter
