What is #pH# for a solution prepared from a #5.7*g# mass of sodium hydroxide that is dissolved in a #100*mL# volume of water?

1 Answer
Sep 30, 2016

Answer:

#pH# is exceptionally high; #pOH# is negative.

Explanation:

#[NaOH]# #=# #(5.7*g)/(40.00*g*mol^-1)# #=# #0.143*mol#. And thus #[HO^-]# #=# #(0.143*mol)/(0.100*L)# #=# #1.43*mol*L^-1#.

Since sodium hydroxide gives quantitative hydroxide ion in aqueous solution, #[HO^-]=1.43*mol*L^-1#.

Now #pOH# #=# #-log_10[HO^-]# #=# #-log_10(1.43)# #=# #-0.154#; this is an exceptionally high concentration of hydroxide ion.

Now #pH+pOH=14# (by definition; see here for the derivation, thus #pH# #=# #14-pOH# #=# #14.15#