Limiting Reactants

A Spreadsheet Problem

 

 

Purpose

 

After completing this activity you will be able to calculate mass-mass relationships in chemical reactions and identify limiting reactants.  You will also develop some skills needed to include formulas in Excel spreadsheets and to construct graphs with trendlines (or best fit lines).

 

 

Activity

 

  1. Write a balanced equation for the reaction between nitrogen gas and hydrogen gas to produce ammonia gas.

 

  1.  Using Excel, create a spreadsheet that calculates the amount of ammonia produced from the above reaction when 100 grams of nitrogen are reacted with hydrogen gas.  Start with 1.00 gram of hydrogen and increase the amount by 1.00-gram increments until you reach 25.0 grams of hydrogen.  Include columns that show:

a.    grams of nitrogen

b.    moles of nitrogen

c.    grams of hydrogen

d.    moles of hydrogen          

e.    moles of ammonia based on N2          

f.      moles of ammonia based on H2          

g.    limiting reactant  

h.    moles of ammonia based on limiting reactant

i.      grams of ammonia based on limiting reactant

j.       grams of excess reactant

 

3.      Construct a graph (scatter plot) that compares grams of hydrogen vs. grams of ammonia produced.  Don’t include the points that show the mass of ammonia is not changing.  In this graph you will include a trendline.  After you have constructed your graph place the curser on one of the data points and right click the mouse.  Select “add trendline” from the menu.  For “type” select linear.  Then click on the “options” tab.  Select “display equation on chart” and “OK.”

 

4.      Construct a second graph that compares moles of hydrogen used to moles of ammonia produced.  Again, don’t include the points that show the mass of ammonia is not changing and include a trendline and equation. 

 

 

Conclusion

 

1.      In your own words define the terms “limiting reactant” and “reactant in excess.”

 

2.      In either graph what is happening at the points where the slope remains zero?

 

3.      The linear regression (trendline) equations for the graphs show that the y-intercept is zero.  Explain.

 

4.      In the equation for graph 1, the slope equals 5.61. 

a.     What is the unit of measurement associated with this number? 

b.     What does this number represent?

 

5.      What is the correct unit of measurement for the slope in the equation for graph 2?

 

6.      How are the slopes of the lines in graph 1 and graph 2 related?