Name:_______________________________________________ Partner: ______________________________________
UN IT 1 Section B: Periodic Trends Lab
Introduction
**Preliminary W ork: Hexane and water do not mix together. W hen they are placed in the same
container, which will float on top of the other? Answer:
**
As you learned earlier, elements were placed in columns on the periodic table because they had similar chemical and
physical properties. In this investigation, you will examine some characteristics of elements from one family. Group
17, which consists of the elements fluorine, chlorine, bromine, iodine and astatine, is called the halogen group.
When elements in this group form compounds, those compounds are known as halide compounds. In this
investigation, you will determine which halogens and halide compounds react with one another and develop a
rule to summarize those interactions.
W hen a halogen gains an electron, giving it a 1- charge, it is called a halide. (F is a halogen
called fluorine, F- is a halide called fluoride)
Procedure
1. Place six clean, dry test tubes in a test tube rack. Mark the test tubes A-F.
Addition of halogen waters (Cl 2 , Br 2 , I 2 ):
2. Add 10 drops of chlorine water (Cl2) to test tubes A and B. Record your observations on page 3 and page 4.
(Caution: The liquids used in this investigation are toxic and irritating to skin. If you spill any liquid on yourself or others,
wash it off thoroughly and ask a classmate to inform your teacher immediately. Avoid inhaling any fumes.)
3. Add 10 drops of bromine water (Br2) to test tubes C and D. Record your observations (pg. 3 and pg. 4).
4. Add 10 drops of iodine water (I2) to test tubes E and F. Record your observations (pg. 3 and pg. 4).
Addition of hexane: (the halogen will be soluble in hexane)
5. Add 20 drops of hexane to each test tube A-F.
6. Mix the liquids together with the “knocking method”. (Holding the top of the test tube tightly with one hand,
tap the bottom of the test tube with the index finger of your other hand with enough force to mix the liquids
together.)
7. Record your observations on pg. 3 and pg. 4, including the number of layers and the color of each layer. See Figure
1.24 on page 64 of your textbook.
Addition of halide compounds (Cl - , Br - , I - ) :
8. Add 10 drops of Br- solution to test tubes A and F. Mix the solutions with the “knocking method”.
9. Add 10 drops of I- solution to tubes B and D and mix each solution.
10. Add 10 drops of Cl- solution to tubes C and E and mix each solution.
11. Record all observations of the mixtures in the test tubes on pg. 3 and pg. 4.
12. Dispose of solutions as instructed by your teacher.
Questions:
1. What did you observe about the halogen waters by themselves?
Cont. on back side…
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2. Do the halogens I2 and Br2 mix more easily with water or with hexane? How do you know?
3. Look at your results for tubes A and B after adding hexane and Br- and I-.
a. Did chlorine water (Cl2) react (remember, a color change is an indication of a chemical reaction)
i. with Br-? ___________
ii. with I-? ___________
b. For each answer to Question 3a, what evidence shows that a chemical reaction did or did not take place?
Cl2 + Br-:
Cl2 + I-:
M aking Claims
Which halogen is most reactive? (That is, it prefers to change its form from halogen to halide.) Give evidence to
support your claim.
Which halogen is least reactive? (That is, it prefers to keep its halogen form.) Give evidence to support your claim.
Construct a general statement to describe the periodic trend of halogen reactivity (that is, what is the trend from most
reactive to least reactive?).
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DATA TABLE
Test tube
Observations
A & B: Chlorine water (Cl2)
C & D: Bromine water (Br2)
E & F: Iodine water (I2)
A & B: Chlorine water (Cl2) after mixing
with hexane
C & D: Bromine water (Br2) after mixing
with hexane
E & F: Iodine water (I2) after mixing with
hexane
A (Cl2) with addition of 0.1 NaBr
B (Cl2) with addition of 0.1 M NaI
C (Br2) with addition of 0.1 NaCl
D (Br2) with addition of 0.1 M NaI
E (I2) with addition of 0.1 M NaCl
F (I2) with addition of 0.1 M NaBr
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Observations:
After addition of 10 drops halogen waters (Cl2, Br2, I2):
A (Cl2)
B (Cl2)
C (Br2)
D (Br2)
E (I2)
F (I2)
D (Br2)
E (I2)
F (I2)
Clâ
Brâ
E (I2)
F (I2)
After addition of 20 drops hexane to each tube:
A (Cl2)
B (Cl2)
C (Br2)
After addition of 10 drops halide compounds (Cl-, Br-, I-):
Brâ
A (Cl2)
Iâ
B (Cl2)
Clâ
C (Br2)
Iâ
D (Br2)
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