Explanation:
(a) The given data is as follows.
B = 
Z = 4 for Be
Now, for the first excited state 
= 2; and 
if it is ionized.
Therefore, ionization energy will be calculated as follows.
I.E = 
= 
Converting this energy into kJ/mol as follows.
= 5249 kJ/mol
Therefore, the ionization energy of the 
ion in its first excited state in kilojoules per mole is 5249 kJ/mol.
(b) Change in ionization energy is as follows.
= 
or, = 
Therefore, wavelength of light given off from the ion by electrons dropping from the fourth (n = 4) to the second (n = 2) energy levels .
I think it’s D hope that helped
0.73 M is the concentration of sulfuric acid that needed 47 mL of 0.39M potassium hydroxide solution to neutralize a 25 mL sample of the sulfuric acid solution.
Explanation:
Data given:
Volume of the base = 47 ml
molarity of the base= 0.39 M
volume of the acid = 25 ml
molarity of the acid =?
For titration reaction between acid and base, the volume or molarity of any of the base or acid can be determined. The formula used:
Macid X Vacid = Vbase x Mbase
Macid = 
putting the values given in the rearranged equation above:
Macid = 
= 0.73 M
The concentration of the sulphuric acid needed is 0.73 M.
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