The Determination of the Mass of a Product of a Chemical Reaction

(Partner: Nina T.)


Observations:

 Day 1: NaCHO3 (Baking Soda) + HCl
                                                 
                                         Before: - very white powder with some clumps
                                           
                                         During: - the NaCHO3 bubbled quickly, then popped with smoke
                                                       - less and less NaCHO3, no chunks       
                                                       - solution becomes milk-like in color
                                                       - NaCHO3 not dissolved in HCl     
                                                       - with each drop of HCl, more and more bubbles appear 
                                                       - solution becomes clearer and less NaCHO3 is visible

Day 2: NaCHO3 (Baking Soda) + HCl --> NaCl + CO2 + H2O

                                                 

                                         Before: - NaCl formed up along sides of beaker

                                                       - yellow at top edges

                                                       - large NaCl bubbles at bottom of beaker
               

                                           

                           

                                            

                                         

                                         During: - the NaCl begins to make a slight pop noise

                                                       - yellow edges at top become light tan

Day 1 Data		Day 2 Data
Mass	Grams	Mass	Grams
Empty 150ml beaker	73.39g	NaCl plus beaker (first weighing)	78.89g
NaHCO3 in beaker	81.19g	NaCl plus beaker (second weighing)	78.85g
		NaCl plus beaker (third weighing)	78.79g

Discussion Questions:


1) Write the grams of NaHCO₃ you had in your beaker.
          81.19g - 73.39g = 7.8g NaHCO₃


2) Calculate how many moles of NaHCO₃ the mass is.
                                                                                     

7.8g NaHCO3	1 mole
	84.02g NaHCO3

= 0.09 mol NaHCO₃ 

3) Write the molar ratio for the NaHCO₃ / NaCl ratio. 

         1 NaHCO₃ : 1 NaCl

4) Write the number of moles of NaCl you predict were produced in your experiment. 

7.8g NaHCO3	1 mol	1 NaCl
	84.02g NaHCO3	1 NaHCO3

= 0.09 mol NaCl 


5) Calculate the mass of NaCl you predict will be produced.

7.8g NaHCO3	1 mol	1 NaCl	58.45g NaCl
	84.02g NaHCO3	1 NaHCO3	1 mol

= 5.43g NaCl

6) Determine, by subtraction, the actual mass of NaCl produced in your experiment. 

   a) First weighing:  78.98g NaCl - 73.39g (mass of beaker) = 5.59g NaCl

   b) Second weighing:  78.85g NaCl - 73.39g = 5.46g NaCl

   c) Third weighing:  78.79g NaCl - 73.39g = 5.40g NaCl

7) Calculate your percentage yield. 

5.4g NaCl

5.43g NaCl x100 = 99% yield

8) What are plausible reasons why your percent yield is less than 100%?

         -We did not use enough NaHCO_3.

9) What are plausible reasons why your percent yield is more than 100%?

         -We used too much NaHCO_3.