Which one gives an acidic pH in aqueous solution ? 1- NaCl 2-NaHCO3 3-Ca3(PO4)2 4-Nh4Cl 5-CH3COOK

To determine, you look at the strength of the underlying acid and base. The stronger one defines the pH of the salt.

##NaCl## strong acid (##HCl##) and strong base (##NaOH##) Result: neutral

##NaHCO_3## weak acid (##H_2CO_3##) strong base (##NaOH##), but with extra (acidic) ##H##. Result slightly alkalinic (##pH~~8.5##)

##Ca_3(PO_4)_2## hardly soluable. Result: near neutral

##NH_4Cl## strong acid (##HCl##), weak base (##NH_4OH##) Result: acidic (but not very much so -- we eat it!)

##CH_3COOK## (potassium acetate) weak acid, strong base (##KOH##) Result: alkalic (but not very)

One more example: ##Na_2CO_3## (washing soda) is very alkalinic (why?).