1. In well i, you allowed the chemical NH 3 and CuSO 4 to react. This reaction p
ID: 788578 • Letter: 1
Question
1. In well i, you allowed the chemical NH3 and CuSO4 to react. This reaction produced a thick, dark blue precipitate known as tetramminecopper(II) sulfate. This chemical was first discovered on copper ammunition cartridges stored near animal excrement. As the ammonia fumes wafted from the feces, it reacted with the copper and damaged the casings. Suppose a sample of this metal was collected from the site for analysis. The researcher began by measuring the mass of a graduated cylinder filled with 10.0 mL of water and found it to be, 14.1 grams. He then placed a chunk of the metal into the cylinder. The volume of the mixture was then recorded to be 11.4 mL and its mass increased to 16.6 grams. What is the density of this metal?
2.A CHE 111 student placed two pipette drops of each liquid chemical combination into one well of the 24-well plate. The chemicals were allowed to react for 1 minute and the following data was recorded. What is the identity of the unknown (pick from one of the chemicals used in this lab)? Please justify your answer with 1-2 sentences explaining your guess. Finally, what follow up step could this student perform to confirm their choice?<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
The phenolphthalein turned the unknown pale pink.
NaHCO3, No reaction seen
Pb(NO3)2, White solid (precipitate formed)
AgNO3, Nothing happened
3. Explaining each physical and chemical change:
A brilliantly colored bright yellow compound, Mercury(II) oxide produces a "quicksilver", a nickname for liquid Mercury, and oxygen gas when heated. Then, the liquid mercury was cooled to -38oC , where it solidified. A smoldering wood splint was then put into the oxygen gas and burst into flame.
Explanation / Answer
1) Volume of the metal chunk = 1.4ml
Mass of the chunk = 2.5 g
Density of metal = 2.5/1.4 g/cc = 1.786 g/cc
2) Phenopthelein test indicates the solution is highly basic.
The white precipitate can then be either lead sulphate or lead hydroxide.
NaHCO3 gives no reaction. hence the precipitate must be lead sulphate
So, the unknown chemical might be Na2SO4
3)Decomposition reaction takes place when HgO is heated releasing oxygen(first oxygen synthesis)
The other product left is Hg which is liquid and shiny silvery at room temperature.
Hg solidifies at -38.83oC
The smoldering wood piece catches fire since, oxygen supports combustion.
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