An atom is the simplest particle that exists and retains the property of the element. A compound is made up of two or more elements chemically combined.
Answer: To answer your question of what is true of a lewis base, it is true that a lewis base donates electron pairs.
Explanation: A Lewis base is any substance, such as the OH- ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an electron-pair donor.
Answer:
The pH of the solution is 2.56.
Explanation:
Given :
Concentration (c) = 0.40 M
Acid dissociation constant = 
The equilibrium reaction for dissociation of 
(weak acid) is,
initially conc. c 0 0
At eqm. 
Dissociation constant is given as:
By solving the terms, we get value of 
No we have to calculate the concentration of hydronium ion or hydrogen ion.
![[H^+]=c\alpha=0.4\times 0.00686832=0.002747 M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3Dc%5Calpha%3D0.4%5Ctimes%200.00686832%3D0.002747%20M)
Now we have to calculate the pH.
![pH=-\log [H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%20%5BH%5E%2B%5D)
Therefore, the pH of the solution is, 2.56.
You did not provide the statements but a possible answer might be that the current atomic theory is sound and that technology that could challenge it does not exist at this time. There is no way to change it because no research can be done about it.
