H3PO4, acid strength

HS04 and H3PO4 are very similar in acid strength Both are much weaker than H2SO4 which IS a strong acid... 

Compare the acid strength of phosphoric acid with that of other common acids. Do all three hydrogen ions of H3PO4 dissociate with equal readiness ... 

Moffat and his co-workers have carried out several studies with phosphate catalysts and Moffat and Riggs prepared BPO4 catalysts for which H3PO4/H3BO3 varied from 1.0 to 1.5 and used them for propan-l-ol dehydration. Surface acidity was determined by n-butylamine titration and the rate constant was observed to increase as surface acidity increased this could have been an effect of either total acid strength or of a narrower range of strengths. It was also concluded that, as acid site concentration decreased with pre-treatment temperature, the main active sites must be Bronsted acid sites. 

Suitable catalysts for cationic polymerization may be conveniently classified into three groups. The classic protonic mineral acids, such as H2SO4, HCIO4, and H3PO4, are often useful. Effective catalysis is obtained if the acid selected has high acid strength, and an anion of low nucleophilicity (Eq. 22.9). 

The pH found in Example 5-2 is quite low, showing that the mercuric ion has the property of a weak acid of approximately the same strength as acetic acid. The acid strength of some metal ions is quite considerable. For example, the pH of equimolar H3PO4 and solutions are similar. The strong acid properties of hydrated metal ions become evident in processes such as coagulation/flocculation, where hydrated aluminum sulfate (alum) or ferric chloride is added to a natural water that is buffered with bicarbonate. The metal ion "titrates" (or reacts with) a stoichiometric amount of alkalinity, just as the addition of an equal amount of strong mineral acid would. 

Two comparisons are discussed in this section (a) the acid strengths of the oxoacids of the second period, H3BO3, H2CO3 and HNO3, and (b) those of the oxoacids of the third period, H3PO4, H2SO4 and HCIO4. 

Phosphorous acid, H3PO3, and phosphoric acid, H3PO4, have approximately the same acid strengths. From this information, and noting the possibility that one or more hydrogen atoms may be directly bonded to the phosphoras atom, draw the structural formula of phosphorous acid. How many grams of sodium hydroxide would be required to completely neutralize 1.00 g of this acid ... 

Suggest a reason why the acid strength decreases with each step in the ionization of phosphoric acid H3PO4 — H2P04 — HPO42-. 

Figure 6.14. Pore volume of activated carbons from white oak and yellow poplar (H3PO4 wood = 1.45 g g", acid strength 28%) (Jagtoyen and Derbyshire, 1998).

Figure 6.23 shows how yield of carbon is a function of HTT for carbons produced with phosphoric acid, compared with runs where the acid was removed before the last 50 °C of heat treatment (H3P04 wood = 1.45gg , acid strength 28%). The H3PO4 promotes a higher yield. 

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