Answer : The concentration of 
ion is, 
Solution : Given,
pH = 4.20
First we have to calculate the pOH.
As we know that,
Now we have to calculate the concentration of ion.
![pOH=-\log [OH^-]](https://tex.z-dn.net/?f=pOH%3D-%5Clog%20%5BOH%5E-%5D)
![9.8=-\log [OH^-]](https://tex.z-dn.net/?f=9.8%3D-%5Clog%20%5BOH%5E-%5D)
![[OH^-]=1.58\times 10^{-10}M](https://tex.z-dn.net/?f=%5BOH%5E-%5D%3D1.58%5Ctimes%2010%5E%7B-10%7DM)
Therefore, the concentration of ion is,
<span>Igneous
rocks are those rocks that were formed through cooling and solidifying the
molten materials. The best example for igneous rock is solid volcanic java.
Lava are liquid that comes from a volcano, but once it is dried and solidify,
it becomes a rock and called igneous rock.
Another example is the granite and basalt. And according to research igneous
rock comes from the latin word ignis which means fire. Thus this says it all.
From a liquid becomes a rock.
</span>
Hello there.
An atom that has the same amount of atoms of each element on both sides of the reaction obeys what law
<span>law of conservation of mass</span>
I think the anwser is A but I'm not sure so I might need to get somebody else's opinion like i said I'm sorry if it's wrong
