aluminum analysis(chemistry)

8/3/2019 Aluminum Analysis(Chemistry)

http://slidepdf.com/reader/full/aluminum-analysischemistry 1/30



To determine the percentage of aluminum in a soft drink

can.



The reaction of an active metal with acid will produce a salt

and hydrogen gas.



` The combination of an active metal with acid will producea salt and hydrogen gas.

2 Al(s) + 6 HCl(aq) 2 AlCl3(aq) + 3 H2(g)

` The gas can be captured, and its quantity determined.

` Using the moles of hydrogen gas and stoichiometry, themass of aluminum can be determined.

` Finally, using the calculated mass of aluminum and the

mass of the aluminum can, the percent purity of thesample can be determined.




223

2

H moles

x

H

Al

!

Moles H2 can be determined using the Ideal Gas Law

PV = nRT



` After using the leveling tank, the pressure in the gasburet is the same as in the room, but the pressure in theburet is due to two gases: hydrogen and water vapor.

` The vapor pressure due to water must be subtracted

from the total pressure (Dalton¶s Law) to give thepressure due to the hydrogen gas.




1. Need to determine the mass of aluminum can required to

make about 40mL of hydrogen gas:

V = 40 mL 0.040L

P = 773.0 ± 21.1 = 751.9 mm Hg 0.9893 atmT = 23oC 296K

2. Using the Ideal gas law, calculate the moles of hydrogen:

PV = nRT

0.9893atm(0.040L) = n(0.08206L-atm mole-1K-1)(296 K)

n = 0.001629 moles H2




3. Determine the moles of aluminum:

223

2

H moles

x

H

Al !




3. Determine the moles of aluminum:

Almoles001086.0x

2Hmoles001629.0

x

2H3

Al2

2Hmoles

x

2H3

Al2

!

!

!




4. Determine the mass of aluminum:

mol)Al(26.98g/moles0.01086Alg !




4. Determine the mass of aluminum:

Alg0293.0)mol/g98.26(Almoles01086.0Alg

!!



1. Weigh out the calculated amount of aluminum can. Put thealuminum scraps into a 10 x 75 mm test tube.

2. Measure 15 mL of 6 M HCl and place it in a 25 x 150 mm test tube.

3. Carefully slide the 10 x 75 mm test tube (containing the aluminum)into the 25 x 150 mm test tube (containing the acid)

4. Put the test tube into a test tube clamp attached to a ring stand. Puta rubber stopper containing a glass and rubber tube attachment onthe 25 x 200 mm test tube.

5. Fill a 50 mL gas buret completely with water.

6. Invert the buret and insert the open end in the beaker. Be sure thatno air enters the buret.

7. Insert the free end of the rubber tube into the gas buret. Be surethere is space between the walls of the gas buret and the tubing.



1. Have your setup approved by your laboratory instructor.2. Tilt the test tube until the acid in the larger test tube flows into the

smaller test tube.

3. When no bubbles have entered the gas buret for two minutes, you

are ready to remove the gas buret.

4. While the buret is still underwater, put your finger over the openend of the partially filled buret.

5. Remove the buret and put the open end (covered with your finger)

into the leveling tank. Do not remove your finger from the buret

until the open end is under the water level in the leveling tank.

6. Raise or lower the gas buret in the leveling tank until the water

level in the tank is even with the water level inside the gas buret.The pressure of the gas in the gas buret is now equal to the

barometric pressure and the volume of the gas buret can be read.



1. The temperature of the gas this is the same as the temperature of the liquid that the gas

bubbled through.

2. Pressure

by using a leveling tank, the pressure in the buret and the roomare assumed to be the same.

the pressure in the buret is the sum of the pressures of H2 and

H2O, by knowing the temperature of the water the pressure of

the H2O can be determined and subtracted.

3. Volume The volume can be correctly read when the pressures are

equalized.



Ptotal = 773 mm Hg (from barometer)

V = 23.5 mL 0.0235L

R = 0.08206 L-atm mol-1K-1

T = 23oC 296K



After using the leveling tank, the pressure in the gasburet is the same as in the room, but the pressure in the

buret is due to two gases: hydrogen and water vapor.

The vapor pressure due to water must be subtracted

from the total pressure (Dalton¶s Law) to give the

pressure due to the hydrogen gas.



After using the leveling tank, the pressure in the gasburet is the same as in the room, but the pressure in the

buret is due to two gases: hydrogen and water vapor.

The vapor pressure due to water must be subtracted

from the total pressure (Dalton¶s Law) to give the

pressure due to the hydrogen gas.

Phydrogen = Ptotal ± Pwater

Phydrogen

= 773mmHg ± 21.1 mmHg

Phydrogen = 751.9mmHg



Phydrogen = 751.9 mmHg 0.9893 atm

V = 23.5 mL 0.0235L

R = 0.08206 L-atm mol-1K-1

T = 23oC 296K



Phydrogen = 751.9 mmHg 0.9893 atm

V = 23.5 mL 0.0235L

R = 0.08206 L-atm mol-1K-1

T = 23oC 296K

PV = nRT

(0.9893atm)(0.0235L) = n(0.08206 L-atm mol-1K-1)(296K)

n = 0.000958 mol H2




Al moles x

H moles

x

H

Al

H moles

x

H

Al

000639.0

000958.03

2

3

2

22

22

!

!

!




Al g mol g Al moles Al g

0172.0)/98.26(000639.0

!!



` All wastes from this experiment can be flushed down the

sink with plenty of running water.



` 6M HCl is corrosive. If you spill any on you, wash the

affected area with water for 5 minutes.

` Neutralize any acid spills with baking soda.

` Hydrogen gas in this experiment is flammable. No open

flames are permitted in the laboratory.

aluminum analysis(chemistry)

Documents