4. A sample consists of one or two of the following salts: Na,CO,, KNO3, CaCl. I

Question

4. A sample consists of one or two of the following salts: Na,CO,, KNO3, CaCl. It is known that the sample completely dissolves in water and when dilute HCl is added to the solution effervescence is observed. You may need to use additional resources (like your text book) to answer these questions Look at the solubility rules; are all of the salts soluble? Write out the equations of the dissolution of each salt. If any of the ions produced from the dissolution of each salt were mixed together would an insoluble precipitate form? If yes, list the salt that would form and why it would not be soluble and list the two original salts that must not both be present. a. b. c.

Explanation / Answer

Solubility rules:

- Most alkali metal (group I metals) are always soluble

- Cations/Anions such as NH4+, HCO3-; ClO3-, NO3- are always soluble

- Most halides are soluble, F-,Cl-,Br-,I-, exceptions = Ag+, Hg2+2, Pb+2 compounds

- Most sulfates are soluble (SO4-2); exceptions = Ag+, Ca+2, Sr+2, Ba+2, Hg2+2, Pb+2 compounds

- In general (except all alkali metals) these ions will NOT be soluble: PO4-3, CrO4-2, S-2, CO3-2

a)

all salts are soluble

b)

Na2CO3 = 2Na+ +CO3-2

KNO3 = K+ + NO3-

CaCl2= Ca+2 + 2Cl-

c)

if effervescence is seen, ther eis CO3- forming CO2(g), then Na2CO3 is present for sure

since no preicpitate is formed, CaCO3 is not formed from Na2CO3 + CaCl2

then, ignore CaCl2, since it is not present

impossible to know is KNO3, since it remains inert

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