Test Tube 2: 6 M NaOH: When samples of this test tube were mixed with samples from test
tube 1, a great deal of heat was produced. The same occurred when I mixed samples of this
tube with test tube 4. Therefore, test tube 2 had to contain a strong base since I had already
identified test tube 1 as a strong acid. The only strong base among the choices was 6 M NaOH.
When I mixed samples from test tube 2 with samples from test tube 10 which I thought con-
tained Ag+, a brownish-gray precipitate was formed, indicative of AgOH. When I mixed sam-
ples of test tube 2 with samples from test tube 7, which I believed contained Sn4+, a precipitate
formed, which I believed to be Sn(OH) 4. Upon adding more solution from test tube 2, the pre-
cipitate dissolved, consistent with a shift in equilibrium. When I mixed samples from test
tube 2 with samples from test tube 6, which I believed contained Ni2+, a green precipitate was
produced, Ni(OH) 2.
Test Tube 3: 6 M NH 3 :I carefully smelled all tubes to begin with and this tube was definitely
ammonia. Since I was able to rule out this tube initially, I then mixed a small amount of known
ammonia with all other tubes. As I mixed the ammonia with the other tubes, I noticed consider-
able heat being produced in tubes 1, 4 and 7, which I suspected was due to an acid present.
With tube 1, smoke appeared, which led me to believe that tube 1 was the HCl which produced
a white cloud (smoke) of NH 4 Cl. Tubes 1 and 3 were now ruled out. I then noticed precipitates
formed in tubes 8 (blue), tube 6 (blue), tube 5 (white), tube 10 (brownish-grey) and tube 7
(white). When excess ammonia was added to tube 10, the precipitate dissolved. When excess
ammonia was added to test tube 8, the precipitate dissolved and the solution turned dark blue
indicative of Cu2+. When I added excess ammonia to test tube 6, the precipitate dissolved and
the solution turned a medium blue color, indicative of the presence of Ni(NH 3 ) 6 2+.
Test Tube 4: 3 M H 2 SO 4 :Test tube 4 had to contain an acid since when I mixed it with test
tube 3 which I had concluded contained a base, it got hot. Since I had already identified test
tube 1 as 6 M HCl I was left with the choice of this tube containing either the 3 M H 2 SO 4 or
SnCl 4 in 3 M HCl. When I mixed test tube 4 with tube 2 the reaction produced a great amount
of heat. Therefore, I concluded that this tube had to contain a strong acid. I was able to rule out
the SnCl 4 earlier (see test tube 7), therefore this tube must have contained the H 2 SO 4.
Test Tube 5: 0.1 M Al(NO 3 ) 3 : When I mixed samples of test tube 5 with a sample from test
tube 3, a white precipitate formed. No heat was evident. The white precipitate could have been
either Al(OH) 3 or Sn(OH) 4 , however, since no heat was produced and the Al(NO 3 ) 3 did not con-
tain an acid, it can be concluded that test tube 5 contained Al(NO 3 ) 3. When I mixed samples of
test tube 5 which I believed contained Al3+with samples of test tube 2 which I believed con-
tained OH–, a white precipitate formed which I believed to be Al(OH) 3. When I added more so-
lution from test tube 2, increasing the OH–concentration, the precipitate dissolved, consistent
with a shift in equilibrium.
Test Tube 6: 0.1 M Ni(NO 3 ) 2 : I was able to identify this tube through observation since the
Ni2+ion is green. No other solution in the list should have had a green color. I was able to con-
firm this when I mixed samples of test tube 6 with test tube 3 (ammonia) producing Ni(NH 3 ) 6 2+,
a known light blue solution. When I mixed samples from test tube 6 with test tube 4 which I
believed to contain OH−, a green precipitate formed consistent with the color of Ni(OH) 2.
Part III: AP Chemistry Laboratory Experiments