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)  + AgNO_{3 (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) + AgNO_{3 (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 1^st or 2^nd item in the respective ratios.

resource

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