SCH3U Name: ____________________________
Purpose : To observe a chemical reaction and to use qualitative and quantitative evidence to identify this reaction from four possibilities.
A) WEAR SAFETY GOGGLES AT ALL TIMES:
Heating any chemical can be hazardous. Material can be ejected from the test tube or explode.
B) Follow all rules for safe Bunsen burner use. Review Bunsen burner safety sheet as needed.
Loose clothing and hair should be secured during the lab.
C) Hot glassware and metal components do not look different from cold ones.
Do not handle equipment until you know it is safe (
).
If burned, place affected area under cold, gently-running water
.
D) Do not point the test tube towards anyone.
Do not walk in front of test tubes while they are being heated.
Test tube must be oriented at a 45 o
angle while heated.
Introduction : In this experiment you will heat a common household chemical, baking soda (sodium hydrogen carbonate, NaHCO
3
). The reaction which occurs is one of the following,
:
NaHC0
NaHC0
3(s)
3(s)
-->
-->
NaOH
Na
2
(s)
C0
3(s)
+
+
C0
2(g)
CO
2(g)
+ H
2
O
(g)
NaHC0
NaHCO
3(s)
3(s)
-->
-->
Na
Na
2
2
0
C
(s)
2
0
4(s)
+
+
CO
2(g)
O
2(g)
+
+
H
H
2
2
O
O
(g)
(g)
You will choose the correct equation based on quantitative observations of the masses of solid reactant and solid product and qualitative observations on the identity of gaseous products.
Materials and Equipment
2 150 mm test tubes test tube clamp
Baking soda Limewater iron ring Bunsen burner wooden splint cobalt chloride paper retort stand
Procedure :
1) Measure and record the mass of one of the test tubes.
Add about 3 g ofNaHCO
3
to this test tube and record the total mass.
2) Half-fill the other test tube with limewater
3) Clamp the NaHCO
3
test tube at a 45 o angle on the stand with the powder at the back, over the Bunsen burner.
Keep the clamp loose enough so that the test tube can be rotated in the clamp.
Make sure that enough of the mouth end of the test tube sticks out from the clamp so that you can grasp it without
touching the metal clamp.
4) Heat the powder gently for 1 minute.
5) As soon as any condensation is seen near the mouth of the test tube, test it with Cobalt chloride paper.
6) Hold the lime water test tube right below the opening of the baking soda test tube for about 60 seconds.
Remove the lime water test tube and gently agitate it. Observe the test tube for any white precipitate.
7) Hold a glowing splint near the mouth of the baking soda test tube and note any reaction.
8) Heat the baking soda test tube for another 6 minutes.
Carefully rotate the test tube to make sure all of the powder comes in contact with the sides of the test tube.
9) Play the flame of the Bunsen burner along the length of the test tube to ensure that any liquid is boiled away.
10) Allow the test tube to cool. Determine the mass of the test tube and residue.
Observations :
Mass of test tube Results of Gas Tests
Mass of test tube and baking soda
Mass of baking soda Lime Water
Mass of test tube and solid product
Actual mass of solid product
Equation
Predicted mass of solid product
1 2
Glowing Splint
Cobalt chloride
3
Percent discrepancy compared to actual mass of solid product
Discussion :
1) What evidence was useful for choosing the correct equation?
2) Which product in the different reactions remained in the test tube?
3) What errors might have significantly affected your conclusion in this experiment?
Conclusion :
Which is the correct equation for this reaction?
4