5. At 20°C, the water autoionization constant, Kw, is 6.8 ´ 10–15. What is the H3O+ concentration in neutral water at this temperature? A. 6.8 × 10–7 M B. 3.4 × 10–15 M C. 6.8 × 10–15 M D. 8.2 × 10–8 M E. 1.0 × 10–7 M

Explanation:

Let us assume that the concentration of [ and is equal to x. Then expression for for the given reaction is as follows.

Now, we will take square root on both the sides as follows.

          M

Thus, we can conclude that the concentration in neutral water at this temperature is M.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8

i think its 100.

hope this !