Reaction stiochiometry

background [prelab assignment (20 points); due at the beginning of the lab]

1.  briefly, describe an experimental procedure to determine:

the amount of Cu consumed [hint: use a balance]

the amount of AgNO3 (i.e. Ag+) consumed [hint:  see lab 3; EF lab]

the amount of Cu(NO3)2 (i.e  Cu2+) generated [ hint: see lab 1; Beer's law].

the amount of Ag generated [hint: use a balance]

in the reaction: Cu (s)  + AgNO3 (aq)  -->  Ag (s)  + Cu(NO3)2 (aq) based on independent experimental data.

2.  sketch a data table for this lab containing entries for all required experimental measurements (i.e. review purpose & content of lab report)

purpose

determine the stoichiometry of the reaction (i.e. coefficients, x, y, z, in the chemical reaction)

x Cu(s) + AgNO3 (aq)  -> y Ag(s) + z Cu(NO3)2 (aq)

based on independent experimental data

material

copper wire (~ 6 inches); 200. mM silver nitrate

test tube; balance; sandpaper (or steel wool); graduated cylinder

filter paper / funnel; beaker; ring stand

colorimeter; aqueous solution of Cu(NO3 )2  [to be prepared by the student]

methods / data analysis

student design; delegate lab work; review the use of the colorimeter prior to the lab

solid copper is added to a solution of silver nitrate the day before (or on the morning of the day of) the experiment

Content of lab report [40 points]

data analysis

data table(s) of your experimental measurements   [5 points]

determination of:  ____  - based on your group's data (show your work)  [20 points]

# moles of copper consumed in the reaction

# moles of silver generated in the reaction

[Cu2+]  (show calibration curve & determination of [Cu2+])

# moles of copper generated in the reaction

the coefficients of chemicals in the chemical reaction, where the value of the coefficient of copper as a product is set to 1

statistical analysis of class data   [5 points]

compare the experimental & expected coefficients in the chemical reaction

• Cu consume : Cu2+ generate
• Ag generate :  Cu2+ generate

error analysis [10 points]

Rationalize potential nontrivial experimental errors and its consequence (be specific:  underestimate ?  overestimate ?  no effect ?) on the mole ratio of

• Cu consume : Cu2+ generate
• Ag generate :  Cu2+ generate

Note that the error may affect either the 1st or 2nd item in the respective ratios.

resource

lab activity source (examples):  site 1  & site 2 [access 4 / 2009]