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Part 1: preparation of alum/quantative analysis (calculation of % yield)

1.     Cut a 5cm x 5cm square piece of aluminum from a scrap aluminum can and sand the paint off using steel wool. 

2.     Cut this piece into smaller pieces (about 0.5 cm long) and weigh out ~1g. Record the weight to 3 decimal places.

3.     Place the aluminum in a 400-mL beaker and add 50 mL of 4 M KOH.

4.     Place beaker on the heating mantle and heat gently.


5.     When the bubbles have stopped, remove from the heat, i.e., hydrogen is no longer evolved.

6.     Vacuum filter the solution and save the filtrate, you may toss out the solid. (Ask your TA if you need instruction in performing a vacuum filtration.)

7.     Carefully rinse your graduated cylinder, pour out 25-30 mL of 9 M H 2 SO 4 size 12{H rSub { size 8{2} } ital "SO" rSub { size 8{4} } } {} and then add slowly to the filtrate.

CAUTION - H 2 SO 4 size 12{H rSub { size 8{2} } ital "SO" rSub { size 8{4} } } {} IS A STRONG ACID AND DEHYDRATOR. SEE TA IMMEDIATELY IF YOU SPILL ANY!

8.     Heat gently while stirring until the solution becomes clear. Boil the solution down to a volume of about 45 mL.

7.     While the solution is boiling, prepare an ice bath by filling a bowl half-way with ice and then adding water until the bowl is three-quarters full.

8.     After the "boiling off", let the beaker cool to room temperature and then place it in the ice bath. Crystals of alum should form. Allow to cool for 15 minutes.

9.     After 15 minutes, vacuum filter the product and wash with 10 mL of ethanol.

10. Allow to dry for a few minutes. Dry completely in the microwave at less than 50% power in 10 sec intervals until the weight no longer changes.

11. Calculate the percent yield and describe the appearance of the crystals.

Part 2: qualitative analysis of alum

1.     Use a straw spatula to transfer a few of the alum crystals (about 5 mg) to a watch glass. Add 3 drops of water to the crystals. Stir gently until the crystals dissolve.

2.     Use a small piece of indicator paper to see whether the solution is acidic, basic, or neutral.

3.     Now add 1 drop of 0.5 M BaCl 2 size 12{ ital "BaCl" rSub { size 8{2} } } {} (barium chloride) to the solution. Record your observations.

4.     A really good test for the presence of potassium is a flame test. Using the hot grips, hold a stainless spatula in the flame of a Bunsen burner to volatilize impurities from the spatula.

5.     When one end of the spatula is red hot, remove it, and quickly touch it to a small cluster of crystals. Several should stick.

6.     Slowly bring the spatula (plus crystals) toward the flame and watch carefully. Hold the crystals in the flame for at least 5 seconds (until the solid glows). Record your observations.

7.     Remove the spatula and place on a non-asbestos mat.

Part 3: acid-base properties of aluminum compounds

Clean 3 test-tubes and label them.

Tube 1:

Place 10 drops of 1M aluminum nitrate solution and 2 drops of 6.0 M sodium hydroxide solution, mix well and record your observations on your lab report Then add more sodium hydroxide solution to tube 1 until a reaction is observed (around 7 drops). Mix well. Record your observations.

Tube 2

Place 10 drops of 1M aluminum nitrate solution and 2 drops of 6.0 M sodium hydroxide solution, mix well and record your observations on your lab report Then add 4 mL of 6M HCl and record your observations.

Tube 3

Add 3 mL of 6M ammonium hydroxide, i.e aqueous ammonia to your alum and record your observations.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
I'm not good at math so would you help me
what is the problem that i will help you to self with?
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
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Source:  OpenStax, General chemistry lab spring. OpenStax CNX. Apr 03, 2009 Download for free at http://cnx.org/content/col10506/1.56
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