[lolelbows]

Hello.  Here is the problem I am having a lot of trouble trying to figure out how to solve.

Water flowing through pipes of carbon steel must be kept at pH 5 or greater to limit corrosion.  If an 8.0 x 10^3 lb/hr water stream contains 10 ppm sulfuric acid and .015% acetic acid, how many pounds per hour of sodium acetate trihydrate must be added to maintain that pH?  Assume that the sulfuric acid completely ionized to SO4.

Here is what I have done to make it accessible:
362.874L solution    3628.74 g H2SO4(molar mass = 98.086)   54.4311 g C2H4O2(molar mass = 60.052)   ?g C2H3O2Na3(H2O) (molar mass = 136.082)

pH=5 .. so we are looking for [H3O]=.00001

H2SO4 <--> 2(H3O) + SO4  so twice as many moles of H30 as of H2SO4.
36.99mol     73.99mol H3O+/362.874L  = .2039 M from that

CH3COOH <--> CH3COO + H3O+  found pka of acetic acid = 1.8x10^-5  made ICE table, mol H3O from acetic acid = .00403 /362.874L = 1.11x10^-5 M from that


And I just don't know where to go from here.  I don't know anything about sodium acetate trihydrate or how it would dissociate and I'm not really sure what to do next at all.  Any help would be appreciated and if you wanted to verify my work up to this point that'd be great as well.

Thanks in advance!!

[Borek]

Sodium acetate is a weak base (more precisely: conjugate base of the acetic acid). You need to add enough to neutralize sulfuric acid and to create a solution of acetate buffer.

No idea where you got mass of the sulfuric acid from, but 10 ppm is not 0.2M in H⁺, you seem to be orders of magnitude off to me.

[lolelbows]

That definitely helps.  Thank you.  Somehow a milligram of h2so4 got turned into a gram.  I was thinking the amount of base I'd have to add might be enormous..

You mentioned sodium acetate being a weak base, but will I just ignore the trihydrate part?  I can't find anything about the Kb of sodium acetate trihydrate.

[Borek]

Fact that it is a trihydrate matters only when calculating molar mass.