Medgar Evers College The City University of New of Go Department of Physical, En
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Question
Medgar Evers College The City University of New of Go Department of Physical, Environment Laborato Prelab an Report sheet Questions 1-001-00 Chemistry (CHML Spring 2017 Hal Laboratory Manual: Laboratory Pearson. 12E, by John H. Nelson Kenneth C. Kemp. 70502.0, ISBN 10: o 321-7oso Experiment 7 Prolab Questions: No Prelab Questions. Report Sheet Questions your unknown. There 3 Postlab Questions similar in the lab to identify Answer to what was done on this sheet. Be Neat. 1 You are given two bottles without label. How would you One contains potassium iodide and another sodium chloride (table salt) as done in the identify these two chemicals (iodide and chloride ion by using reaction lab. You should know chemical formulas of these compounds. a) Initial reactions of both with conc Hzsoa. Describe the reaction of each and explain how will you identify each bottle. Read lab manual.Explanation / Answer
1a) Chloride and iodide ions both react with concentrated sulfuric acid (H2SO4). Chloride ions produce steamy white fumes of hydrogen chloride (HCl) while iodide produces white fumes of hydrogen iodide (HI) contaminated with purple fumes of iodine (I2). What is most likely to be observed are the purple vapors of iodine. The reactions taking place are
2 NaCl (aq) + H2SO4 (conc.) ------> Na2SO4 (aq) + 2 HCl (g, white fumes)
2 KI (aq) + H2SO4 (conc.) ------> K2SO4 (aq) + 2 HI (g, white fumes)
2KI (aq) + 2 H2SO4 (conc.) ------> 2 KHSO4 (aq) + I2 (g, purple) + H2 (g, white)
b) The two halide ions can be identified easily by testing with an aqueous solution of silver nitrate (AgNO3). Both NaCl and KI are acidified using dilute nitric acid followed by the addition of silver nitrate solution. AgNO3 reacts with NaCl to give a white precipitate of silver chloride (AgCl) that remains insoluble in nitric acid. KI reacts with AgNO3 to given a pale yellow precipitate of silver iodide (AgI). AgI is insoluble in dilute nitric acid.
NaCl (aq) + AgNO3 (aq) -------> NaNO3 (aq) + AgCl (s, white)
KI (aq) + AgNO3 (aq) ------> KNO3 (aq) + AgI (s, yellow)
The precipitate of AgCl is soluble in ammonia (NH3) while AgI is insoluble in NH3.
2a) The aqueous solutions of both sodium bicarbonate (NaHCO3) and sodium chloride (NaCl) are treated with conc. H2SO4. NaCl reacts with H2SO4 to give white fumes of hydrogen chloride (HCl). NaHCO3 reacts with H2SO4 to evolve CO2 gas. CO2 can be easily identified by effervescence occurring inside the reaction tube. The effervescence continues till all the NaHCO3 has reacted.
2 NaCl (aq) + H2SO4 (conc.) -------> Na2SO4 (aq) + 2 HCl (g, white fumes)
2 NaHCO3 (aq) + H2SO4 (conc.) -----> 2 NaHSO4 (aq) + CO2 (g, effervescence) + H2O (l)
b) NaHCO3 and NaCl can be distinguished by treating with a solution of barium chloride, BaCl2 in dilute HCl medium. NaHCO3 will react with BaCl2 to give a white precipitate of barium carbonate (BaCO3). BaCO3 reacts with dilute HCl to liberate CO2.
NaCl doesn’t react with BaCl2 solution.
BaCl2 (aq) + 2 NaHCO3 (aq) ----------> BaCO3 (s, white) + 2 NaCl (aq) + CO2 (g) + H2O (l)
BaCO3 (s) + 2 HCl (aq) ------> BaCl2 (aq) + CO2 (g) + H2O (l)