Question

2 Ag+ + Cu --> Cu+2 + 2 Ag
You individually weigh out a piece of Copper Wire and an empty Reaction Tube. You add a measured volume of silver nitrate solution of known concentration to the Reaction Tube and drop in the copper wire.
Weight of copper wire 1.3771 g
Weight of empty Reaction Tube 6.4591 g
Volume of AgNO3 solution used 3.65 mL
Molarity of original AgNO3 solution 0.1536 M

While the silver is being reduced, you make the following spectroscopic measurements. The blank is distilled water. The STANDARD is made by pipetting 1.00 ml of the original standard into a cuvet and adding exactly 5.00 mL of ammonia + distilled water to give a total volume in the cuvet of 6.00 mL.
%T of Blank 99.1 %
Concentration of original Cu Standard 0.0361 M
%T of Cu Standard in cuvet 39.0 %

After the reaction is complete, 2.35 ml of 14 M ammonia is added to the Reaction Tube to give a total of 6.00 mL of blue solution. 1.00 mL is pipetted into the cuvet and 5.00 mL of ammonia and distilled water were added. The %T of this mixed homogeneous solution was measured in the spectrometer.
The mass of the remaining copper wire was measured
The precipitated silver metal in the Reaction Tube was washed with distilled water and dried and the reaction tube with silver crystals was weighed.
%T of Cu ion in Reaction Tube 24.8 %
Mass of Cu Wire after reaction 1.3579 g
Mass of dried Reaction Tube with Silver metal after reaction 6.5240 g
Calculate:
a) Mass of Silver Metal produced ______________ mg
b) Millimoles of Ag + used up ______________ mmol
c) Atomic Weight of Silver based on silver used up ______________ g/mol
d) Mass of Copper Metal lost from wire ______________ mg
e) Atomic Weight of Silver based on copper metal lost ______________ g/mol
f) Absorbance of Cu +2 standard ______________
g) Absorbance of Cu+2 in Reaction Tube ______________
h) Molarity of Cu+2 in Reaction Tube ______________ M
i) Millimole of Cu+2 in Reaction Tube ______________ mmol
j) Atomic Weight of Silver based on Cu+2 produced ______________ g/mol

Answer 1

a) Mass of silver metal produced = mass of dried Reaction Tube with Silver metal - mass of dried Reaction Tube

                                                   = 6.5240- 6.4591g = 0.0649g = 64.9mg

b- mmol of Ag+ used up = 64.9/107.8682 = 0.60166mmol

c- Atomic Weight of Silver based on silver used up = 64.9 / 0.60166= 107.86823 g/mol

d) Mass of Copper Metal lost from wire = 1.3771g -1.3579 = 0.0192g= 19.2 mg

e) Atomic Weight of Silver based on copper metal lost 107.3969g/mol

there are 2 moles of Ag for every mole of Cu2+ produced

thus moles of Ag = moles of Cu²⁺ x 2 = 19.2/63.546 x2 =0.302143329x2=0.6043 mmol

molar mass= 64.9 / 0.6043=107.3969 g/mol

i) Millimole of Cu+2 in Reaction Tube 0.6043 mmol

f) Absorbance of Cu +2 standard= 2-log39= 0.408935

g) Absorbance of Cu+2 in Reaction Tube

A= 2-log%T= 2- log24.8= 2-1.39445=0.6055