|
View Full Version : Salt Q tizom 05-24-2009, 05:24 PM Which of the following salts will form a pH < 7 ? NH4NO2 NaCl AlCl3 LiBr Na2CO3 FeCL3 or more than one i know the answer, but i am having trouble figuring out why. please explain! PooyaH 05-24-2009, 05:27 PM Which of the following salts will form a pH < 7 ? NH4NO2 NaCl AlCl3 LiBr Na2CO3 FeCL3 or more than one i know the answer, but i am having trouble figuring out why. please explain! Isn't it AlCl3? Just react each one with water! AlCl3 + H2O -> Al(OH)3 + HCl (you know HCl is very acidic and Al(OH)3 is a weak base) so the pH would be less than 7 The rest of them would give you strong acid and strong base (except the last one) which would give a pH of 7! If the question asked which one would give a pH of greater than 7, and KF was one of the answer choices then the answer would have been KF: KF + H2O -> HF + KOH (KOH is a strong base and HF is a weak acid, therefore the solution would be more basic) Actually NaCO3 would be more basic too! iwannabadentist 05-24-2009, 05:30 PM is it AlCl3 and FeCl3? PooyaH 05-24-2009, 05:36 PM is it AlCl3 and FeCl3? Yeah I didn't see the last one! FeCl3 would react the same way as AlCl3 would tizom 05-24-2009, 05:41 PM its FeCl3 AlCl3 and NH4NO3 i didnt understand :( it says NO3 is a spectator ion, and NH4+ + H20 -> NH3 + H3O+ iwannabadentist 05-24-2009, 05:55 PM i guess that makes sense...but i would never have been able to come up with that on my own :-\ sweetcinuhstix 05-24-2009, 07:01 PM its FeCl3 AlCl3 and NH4NO3 i didnt understand :( it says NO3 is a spectator ion, and NH4+ + H20 -> NH3 + H3O+ FeCl3 Fe=lead=precipitate Cl3+H20=HCL! strong acid! Al=aluminum=precipitate Cl3+H20=HCL! strong acid! NH4NO3 NH4=like you said NO3=spectator ions, also include sulfate, perchlorate. Spectator ions appear on both sides of the <-->. |