Chap17 PRS Solubility Rules for Some Ionic Compounds in Water Soluble compounds

Question

Chap17 PRS

Solubility Rules for Some Ionic Compounds in Water

Soluble compounds are defined as those that dissolve to the extent of 1 g or more per 100 g water.
NOT soluble compounds are further classified as:
-Slightly soluble, which dissolve to the extent of 0.01 g to 1 g per 100 g water.
-Difficultly soluble or Insoluble, for which less than 0.01 g per 100 g water will dissolve.

1) Write the dissolution reaction for cobalt(II) hydroxide in water.

Use the pull-down menus to specify the state of each reactant and product.

Is cobalt(II) hydroxide considered soluble or not soluble ? ...  
... A. Soluble
... B. Not soluble

Based upon this, the equilibrium constant for this reaction will be: ...  
... A. Greater than 1
... B. Less than 1

2)Write the precipitation reaction for aluminum hydroxide in aqueous solution:

Use the pull-down menus to specify the state of each reactant and product.

Is aluminum hydroxide considered soluble or not soluble ? ...
... A. Soluble
... B. Not soluble

3) The value of the Solubility Product Constant for lead phosphate is  

Write the reaction that corresponds to this Ksp value.

Ksp values are found by clicking on the "Tables" link.
Use the pull-down menus to specify the state of each reactant or product.
If a box is not needed leave it blank.

Soluble Ionic Compounds 1. All sodium (Na+), potassium (K+), and ammonium (NH4+) salts are SOLUBLE. 2. All nitrate (NO3-), acetate (CH3CO2-), chlorate (ClO3-), and perchlorate (ClO4-) salts are SOLUBLE. 3. All chloride (Cl-), bromide (Br-), and iodide (I-) salts are SOLUBLE — EXCEPT those containing: lead, silver, or mercury (I) (Pb2+, Ag+, Hg22+) which are NOT soluble. 4. All sulfate (SO42-) salts are SOLUBLE — EXCEPT those containing: calcium, silver, mercury (I), strontium, barium, or lead (Ca2+, Ag+, Hg22+, Sr2+, Ba2+, Pb2+) which are NOT soluble. Not Soluble Ionic Compounds 5. Hydroxide (OH-) and oxide (O2-) compounds are NOT SOLUBLE — EXCEPT those containing: sodium, potassium, or barium (Na+, K+, Ba2+) which are soluble. 6. Sulfide (S2-) salts are NOT SOLUBLE — EXCEPT those containing: sodium, potassium, ammonium, or barium (Na+, K+, NH4+, Ba2+) which are soluble. 7. Carbonate (CO32-) and phosphate (PO43-) salts are NOT SOLUBLE — EXCEPT those containing: sodium, potassium, or ammonium (Na+, K+, NH4+) which are soluble.

Explanation / Answer

Ca(OH)2(s) --> Ca+2 (aq) + 2 OH- (aq)

Cobalt hydroxide is not soluble. Because, in the above given information point no 5 states follows.

Hydroxide (OH-) and oxide (O2-) compounds are NOT SOLUBLE — EXCEPT those containing: sodium, potassium, or barium (Na+, K+, Ba2+) which are soluble.

The equilibrium constant for this reaction would be greater than for the common ion effect.

Al(OH)3(s)                        Al+3 (aq)+ 3OH-(aq.)

Aluminium hydroxide is also insoluble for the above mentioned reason

Pb3(PO4)2 (s)                            3Pb+2 (aq)+ 2 PO4(aq)

Ksp =        [Pb+2]3× [PO4]2/ [Pb3(PO4)2]     

Since the concentration of lead phosphate is one, the denominator becomes one and therefore, Ksp of this particular salt is the product of the concentrations of the [Pb+2]3 and [PO4]2.

i.e. Ksp =        [Pb+2]3× [PO4]2

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