which of the following is not soluble ?
(1)sodium chromate
(2)lead(II)iodide
(3)lithium hydroxide
(4)ammonium sulfate
don't understand, please help.
You need to know the solubility rules. Here is a simplified set.
http://www.files.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html
To determine which substance is not soluble, we need to know the solubility rules. Solubility refers to the ability of a substance to dissolve in a solvent, usually water. In general, "like dissolves like," so substances with similar polarities are more likely to be soluble in one another.
One common set of solubility rules for inorganic compounds is as follows:
1. All sodium (Na+), potassium (K+), and ammonium (NH4+) salts are soluble.
2. Most nitrate (NO3-) salts are soluble.
3. Most chloride (Cl-), bromide (Br-), and iodide (I-) salts are soluble, except when paired with silver (Ag+), lead (Pb2+), or mercury (Hg2+) ions.
4. Most sulfate (SO42-) salts are soluble, except when paired with calcium (Ca2+), strontium (Sr2+), barium (Ba2+), lead (Pb2+), or silver (Ag+) ions.
5. Most hydroxide (OH-) salts are slightly soluble, except when paired with sodium (Na+), potassium (K+), or ammonium (NH4+) ions.
6. Most sulfide (S2-) salts are slightly soluble, except when paired with calcium (Ca2+), strontium (Sr2+), barium (Ba2+), sodium (Na+), potassium (K+), or ammonium (NH4+) ions.
Now let's analyze the given substances:
(1) Sodium chromate: According to rule 1, sodium salts are soluble. Therefore, sodium chromate is soluble.
(2) Lead(II) iodide: According to rule 3, most iodide salts are soluble, except when paired with lead (Pb2+) ions. Therefore, lead(II) iodide is not soluble.
(3) Lithium hydroxide: According to rule 5, hydroxide salts are slightly soluble, except when paired with sodium (Na+), potassium (K+), or ammonium (NH4+) ions. Therefore, lithium hydroxide is soluble.
(4) Ammonium sulfate: According to rule 1, ammonium salts are soluble. Therefore, ammonium sulfate is soluble.
Based on the solubility rules, the substance that is not soluble is (2) lead(II) iodide.