Some chemical compounds such as NaCl dissolve in water very well. But some are not. They are deposited as a precipitate at the bottom of the solution. However every compound has a limit to dissolve in water.
|Compound||Solubility in water (g/100ml of water)|
Solubility of silver chloride is much lower than solubility of sodium chloride in the water.
After that maximum limit, the compound does not dissolve in water furthermore and deposit on the bottom of the solution. You can see two separate parts in the aqueous solution.
Example: There is a 100 ml of distilled water. You add NaCl multiple times until see a precipitate.
In this tutorial, we are going to discuss followings.
Solubility is expressed as maximum dissolving mass in unit volume of water.
When temperature increases dissolving amount (solubility) increases.
Maximum amount of mass of the compound which can dissolve in a unit volume of solvent. Usually we express solubility as grams per 100ml of water (g/100ml).
Most of the s block metals' compounds are soluble in water. Lithium forms some insoluble compounds. Lithium carbonate, lithium fluoride and lithium phosphate are insoluble in water.
Solubility of NaHCO3 is low when compared to KHCO3. This phenomenon is used in solvay process to manufacture sodium carbonate.
Alkali earth metals form insoluble and soluble compounds.
According to the anion, solubility is changed. This is very important in qualitative analysis of inorganic compounds.
Silver nitrate is a soluble compound and silver chloride is a white precipitate.
All metal nitrates and nitrites are soluble in water. NaNO3, Al(NO3)3, Fe(NO3)3, NaNO2 are some example nitrate and nitrite compounds which dissolve very well in water.
Some sulfate of 3d metal ions are soluble in water.
PbSO4 is also a white precipitate and does not dissolve in water.
|3d Metal Sulfate||Solubility in water|
|Cr2(SO4)3||Practically insoluble in water|
|MnSO4||52 g/100 cm3 at 50C|
|FeSO4||Soluble in water.|
|Fe2(SO4)3||Slowly sol in water; |
|NiSO4||29.3 g/100 cm3 at 00C
83.7 g/100 cm3 at 100 0C
|CuSO4||Very soluble in hot water,
soluble in cold water
243 g/l at 00C
75.4 g/100 cm3 at 1000C
|ZnSO4||57.7 g/100 g water at 250C
101 g/100 g of water at 700C
Only lithium carbonate is the insoluble carbonate in the alkali metal carbonates. All alkali earth metal carbonates are insoluble in the water.
3d metal carbonates are also insoluble in water.
Solubility of metal carbonates can be used to identify metals by determining the compound is a aqueous solution or precipitate.
|Metal Carbonate||Solubility in water|
|Li2CO3||Solubility is low. Following solubility are expressed as w/w%.
1.52 at 00C
1.31 at 200C
1.16 at 400C
1.00 at 600C
0.84 at 800C
0.71 at 1000C
|Na2CO3||30.7 g/100 g of water at 250C|
105.5 at 0C
108.0 at 100C
110.5 at 200C
113.7 at 300C
155.7 at 1000C
Some metal halides such as NaCl, NaBr or KCl have a high solubility in water. But some metals such as lead or silver will make precipitates with halide ion. These behaviors can be used to identify halide ions compounds.
|Metal Chloride||Solubility in water|
|AgCl||0.520 mg/100 g at 500C - Insoluble in water|
|AgBr||0.14 mg/l at 200C - insoluble in water|
|AgI||3*10−7g/100 ml of water at 200C|
|PbCl2||Insoluble in water
0.673 g/100 ml water at 00C
0.99 g/100 ml water at 200C
3.34 g/100 ml water at 1000C
|PbBr2||0.455 g/100 ml at 00C
0.973 g/100 ml at 200C 4.41 g/100 ml at 1000C
0.044 g/100 ml at 00C
0.0756 g/100 ml 200C)
0.41 g/100 ml 1000C
All alkali metal sulfide compounds and alkali earth metal sulfide are soluble in water. But some metal sulfide compounds' solubility is low and have colours too. These colours are very useful in qualitative analysis of identify sulfide anion.
|Metal Sulfide||Solubility in water|
soluble in water
18.6 g/100 g of water at 200C
29.0 g/100 g of water at 400C
35.7 g/100 g of water at 480C
39.0 g/100 g of water at 500C
You know NaOH or KOH are very strong bases and dissolve very well in the water. But all metal hydroxides are not soluble in water and not strong bases too.
Alkali metal hydroxide are soluble in water and strong bases. But, from alkali earth metal hydroxides, only strontium hydroxide and barium hydroxide are soluble and strong bases.
All 3d metal hydroxides are insoluble in water and have less solubility. Special thing is most of the that hydroxides have colours.
Example: Maximum 22.7g of solid compound A dissolve in 250ml of water.