ANALYSIS FOR IONS   Name __________________________  Section _________ Date _______________   Determination of Cation and Anion of Unknown Salt   Although you are most familiar with table salt, which is the salt used in cooking and seasoning of foods, the family of "salts" has many members. Most are found in nature, such as the chlorides of sodium, potassium and calcium, but all can be formed in the laboratory as a product of a neutralization reaction, that is a reaction between an acid and a base in water. The formation of table salt, NaCl, results by reacting hydrochloric acid and sodium hydroxide as represented by the following equation:                                     HCl(aq)  +  NaOH(aq)  →  NaCl(aq)  +  H2O(l) Your unknown salt contains only one cation. It may be any one of the following four:                                                  Na+, K+, Ca2+ or Fe3+ Your unknown salt contains only one anion. It may be any one of the following four:                                                  CO32-, Cl-, SO42- or PO43- Thus, there are many possible combinations, and you must determine which salt is the unknown given to you.   Testing for the Cation of the Unknown Salt   You should observe only one positive test for the cation in your unknown.   a) In a flame tests for Na+, K+, Ca2+, the color of the flame is bright yellow, violet, or orange-red, respectively. However, the orange-red flame for calcium may not be very prominent. Thus, calcium will require a confirmatory test, and will form a white precipitate when treated with ammonium oxalate (NH4)2C2O4. When a salt containing Fe3+ is treated with potassium thiocyanate (KSCN) solution, a blood-red colored solution will form. By now you should have determined which cation is present in your   Testing for the Anion of the Unknown Salt   You should observe only one positive test for the anion in your unknown.   Any salt containing CO32- ions will react promptly with an acid (e.g., HCl(aq)) to form carbon dioxide gas, which will foam and bubble up in the test tube. If the unknown solution immediately forms a white precipitate when mixed with silver nitrate (AgNO3), and if the precipitate is permanent (that is, it cannot be dissolved in nitric acid), then it proves that chloride ion (Cl-) is present.  Sulfate ions will form a permanent white precipitate when treated with barium chloride (BaCl2(aq)) and nitric acid (HNO3). The proof that PO43- ions are present is the formation of a bright yellow precipitate when a phosphate salt is treated with ammonium molybdate, ((NH4)2MoO4) and nitric acid (HNO3). A positive result would indicate which anion? By now you should have determined what anion is present in your 3. Conclusion         The report form contains observations that were made by one of your classmates. Based on these observations, fill in the blanks to indicate if the ions are present or absent. From the overall set of observations decide which of the salts is your unknown by giving its cation and anion, formula, and name at the end of the report sheet.   Deliverable   Name __________________________  Section _________ Date _______________ Unknown Sample #______XYZ__________ PART A:  CATION TESTS   OPERATION OBSERVATION CONCLUSION Section 1:  Flame test for Na+, K+ and Ca2+ ions     NaCl Bright yellow   KCl Lavender   CaCl2 Not very evident   Flame test for unknown Bright yellow         Section 2:  Test for Ca2+ ions     (NH4)2C2O4 with NaCl Clear solution   (NH4)2C2O4 with KCl Clear solution   (NH4)2C2O4 with CaCl2 White precipitate   (NH4)2C2O4 with FeCl3 Clear solution   (NH4)2C2O4  with unknown Clear solution         Section 2:  Test for Fe3+ ions     KSCN with NaCl Clear solution   KSCN with KCl Clear solution   KSCN with CaCl2 Clear solution   KSCN with FeCl3 Blood red precipitate   KSCN with unknown Clear solution                     I just need the conclusion part after the observation

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ANALYSIS FOR IONS

 

Name __________________________  Section _________ Date _______________

 

Determination of Cation and Anion of Unknown Salt

 

Although you are most familiar with table salt, which is the salt used in cooking and seasoning of foods, the family of "salts" has many members. Most are found in nature, such as the chlorides of sodium, potassium and calcium, but all can be formed in the laboratory as a product of a neutralization reaction, that is a reaction between an acid and a base in water. The formation of table salt, NaCl, results by reacting hydrochloric acid and sodium hydroxide as represented by the following equation:

                                    HCl(aq)  +  NaOH(aq)  →  NaCl(aq)  +  H2O(l)

Your unknown salt contains only one cation. It may be any one of the following four:

                                                 Na+, K+, Ca2+ or Fe3+

Your unknown salt contains only one anion. It may be any one of the following four:

                                                 CO32-, Cl-, SO42- or PO43-

Thus, there are many possible combinations, and you must determine which salt is the unknown given to you.

 

  1. Testing for the Cation of the Unknown Salt

 

You should observe only one positive test for the cation in your unknown.

 

  1. a) In a flame tests for Na+, K+, Ca2+, the color of the flame is bright yellow, violet, or orange-red, respectively. However, the orange-red flame for calcium may not be very prominent.
  2. Thus, calcium will require a confirmatory test, and will form a white precipitate when treated with ammonium oxalate (NH4)2C2O4.
  3. When a salt containing Fe3+ is treated with potassium thiocyanate (KSCN) solution, a blood-red colored solution will form.
  4. By now you should have determined which cation is present in your

 

  1. Testing for the Anion of the Unknown Salt

 

You should observe only one positive test for the anion in your unknown.

 

  1. Any salt containing CO32- ions will react promptly with an acid (e.g., HCl(aq)) to form carbon dioxide gas, which will foam and bubble up in the test tube.
  2. If the unknown solution immediately forms a white precipitate when mixed with silver nitrate (AgNO3), and if the precipitate is permanent (that is, it cannot be dissolved in nitric acid), then it proves that chloride ion (Cl-) is present. 
  3. Sulfate ions will form a permanent white precipitate when treated with barium chloride (BaCl2(aq)) and nitric acid (HNO3).
  4. The proof that PO43- ions are present is the formation of a bright yellow precipitate when a phosphate salt is treated with ammonium molybdate, ((NH4)2MoO4) and nitric acid (HNO3). A positive result would indicate which anion?
  5. By now you should have determined what anion is present in your
  6. 3. Conclusion

 

      The report form contains observations that were made by one of your classmates. Based on these observations, fill in the blanks to indicate if the ions are present or absent. From the overall set of observations decide which of the salts is your unknown by giving its cation and anion, formula, and name at the end of the report sheet.

 

  1. Deliverable

 

Name __________________________  Section _________ Date _______________ Unknown Sample #______XYZ__________

PART A:  CATION TESTS

 

OPERATION

OBSERVATION

CONCLUSION

Section 1:  Flame test for Na+, K+ and Ca2+ ions

 

 

NaCl

Bright yellow

 

KCl

Lavender

 

CaCl2

Not very evident

 

Flame test for unknown

Bright yellow

 

 

 

 

Section 2:  Test for Ca2+ ions

 

 

(NH4)2C2O4 with NaCl

Clear solution

 

(NH4)2C2O4 with KCl

Clear solution

 

(NH4)2C2O4 with CaCl2

White precipitate

 

(NH4)2C2O4 with FeCl3

Clear solution

 

(NH4)2C2O4  with unknown

Clear solution

 

 

 

 

Section 2:  Test for Fe3+ ions

 

 

KSCN with NaCl

Clear solution

 

KSCN with KCl

Clear solution

 

KSCN with CaCl2

Clear solution

 

KSCN with FeCl3

Blood red precipitate

 

KSCN with unknown

Clear solution

 

             

 

 

I just need the conclusion part after the observation 

 

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