Which of the following aqueous solutions
should form a precipitate with aqueous
Fe(NO3)3?
1. KCl
2. KNO3
3. KOH
4. K2SO4
http://www.files.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html
see rule 5, note rule 3.
You need to make flash cards of these rules, and memorize them.
it's not 2
the answer is 3. KOH
To determine which of the given aqueous solutions should form a precipitate with aqueous Fe(NO3)3, we need to consider the solubility rules and check if any of the possible combinations will result in an insoluble compound, which will precipitate.
Here are the solubility rules for some common ionic compounds:
1. Most chloride (Cl-) salts are soluble, except for those with Ag+, Pb2+, and Hg2 2+.
2. Most nitrate (NO3-) salts are soluble.
3. Most hydroxide (OH-) salts are sparingly soluble, except for those with Group 1 cations (e.g., K+) and ammonium (NH4+).
4. Most sulfate (SO42-) salts are soluble, except for those with Ba2+, Pb2+, Sr2+, and Ca2+.
Now, let's go through each of the given options and see which one should form a precipitate with Fe(NO3)3:
1. KCl: According to the solubility rules, chloride salts are mostly soluble. Therefore, it is unlikely to form a precipitate with Fe(NO3)3.
2. KNO3: Nitrate salts are generally soluble, so this is not expected to form a precipitate with Fe(NO3)3.
3. KOH: Hydroxide salts are sparingly soluble, except for those with Group 1 cations (such as K+). This means that KOH would not form a precipitate with Fe(NO3)3.
4. K2SO4: Sulfate salts are mostly soluble, but Fe3+ is an exception. Fe(NO3)3 reacts with sulfate ions (SO42-) to form an insoluble compound, Fe2(SO4)3. Therefore, K2SO4 is the most likely solution to form a precipitate with Fe(NO3)3.
So, the correct answer is: 4. K2SO4.