l. Use your knowledge of solubility rules and predicting products of chemical re
ID: 489818 • Letter: L
Question
l. Use your knowledge of solubility rules and predicting products of chemical reactions to answer the following questions. a. An unknown solid contained either Na,CO,or NH4NO3 The unknown solid gave off a gas when 3-4 drops of concentrated H2SO was added. Is the unknown solid NarCosor NH NO,? What is the chemical identity of the gas evolved? What confirmatory test could be used? b. An unknown solid contained either K,Co, or Ku. An aqueous solution of the unknown. solid produced a white precipitate when 3-4 drops of Ba(OH)2 was added. Is the unknown solid K.CO3 or KI? What is the chemical identity of the white precipitate? c. An unknown solid contained either NaCl or NH NO3. An aqueous solution of the unknown solid produced a precipitate upon addition of AgNO,(aq). Is the unknown solid NaCl or NHNO? What is the chemical identity of the precipitate? What confirmatory test could be used? d. An unknown solid contained either K2CO, or Na2SO4. An aqueous solution of the unknown solid produced a white precipitate upon addition of BaCl2(aq). Is the unknown solid K2CO3 or Naso? Is addition of Bacl a good method for distinguishing Co, from Soia? Why or why not? e. An unknown solid contained either Na2so, or NH Clou. The unknown solid gave off a gas when 3-4 drops of dilute NaoH was added. Is the unknown solid NazSO4 or NHClou? What is the chemical identity of the gas? What confirmatory test could be used?Explanation / Answer
a)
As the unknown solid gave off the gas after addition of concentrated H2SO4, it confirms presence of CO3 2-.
Addition of Ba(OH)2 should be used as confirmatory test.
b)
White ppt after addition of Ba(OH)2 confirms presence of CO3 2-. It is K2CO3.
c)
Precipitation upon addition of AgNO3 confirms Cl-.
Adding conc.NH3 after centrifuge is a confirmatory test.
d)
Precipitation after addition of BaCl2 indicates SO4 2-. Therefore, Na2SO4.
Additin of BaCl2 is not a good method as Cl can give false result as CO3 2-. Another test with conc.NH3 must be taken.
e)
As gas was evolved it may be NH4ClO4. Confirm with wet red litmus.
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