Question

what is the concentration of hydronium ions in soution at 25 degree centigrade with ph =4

Answer 1

Hi friend,
pH=-log(H+) 
So,H+=-antilog(pH)
     H+=-antilog(4)
     H+=1x10^-4.
HOPE THIS HELPS.....

Answer 2

We know that 

pH=-log(H+)  

⇒(H+)=-anti log(pH)

    (H+)=-anti log(4)

    (H+)=1x$10^{-4}$

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Best of luck ;)
ROYALJATT