Experiment date: 2013/12/13
- Principle:
We want to make zinc reaction with acid but not the iron. So we can use the volumetric of H2 to know how many Zn is used. Dalton's law, means the pressure of a mixture of gases can be disperse by the amount of every gas. Like the follow formula:
Ptotal=p1+p2+p3+…+pn
But Dalton's law is not exactitude. Because it is not a law follow the real gases. It is following the Ideal gas law.
Ideal gas law is a often using low and as know as PV = nRT.
- Chemicals and their Properties:
|
H2SO4 (CAS 7664-93-9): |
167.0005 g/mol d:1.84g/cm3 mp: 10 °C bp: 337 °C |
|
Zinc(CAS 7440-66-6): |
65.39 g/mol d: 7.14g/cm3 mp: 419.53 °C bp: 907°C |
|
Zinc Sulfate with 7 water (CAS 7446-20-0): |
287.53 g/mol d: 3.8 g/cm3 mp: 680 °C start to decompose |
|
Iron Metal (CAS 7439-89-6): |
55.845 g/mol d: 7.874g/cm3 mp: 1538 °C bp: 2862°C |
|
Iron(II) Sulfate (CAS 7720-78-7): |
278.05 g/mol(7H2O) d: 1.898 g/cm3 mp: 64°C bp: 90°C |
|
H2 (1333-74-0): |
d: 0.08988 g/L mp: -259.14°C bp: -252.87 °C |
- Tools:
1. Iron nails
2. Iron wire
3. Tubes
4. Beakers
- Safety and Waste Disposal:
Safety :
- Sulfuric acid can damage your eyes, skin, or the cloth. If you touched it, use water to wash it for at least 15 minutes. And tell the teacher as fast as possible. And don’t add water into acid.
- Zinc is normally safe, but it can generate H2 if it contacted with acid.
- Zinc sulfate may cause some irritation if you swallow it. Wash the place you touched with soup and water.
- H2 is easy to burn.
Waste Disposal:
- Galvanized iron wire and nail reacted: recycle or just put in a trash can.
- Unused acid: Add phenolphthalein and neutralize with 1 M NaOH (first appearance of permanent pink color). Flush resulting solution down the sink with running water.
- Reacted solution: recycle in a bottle with word “zinc ion”.
- Procedure:
Part. A (Find good H2SO4)
- Prepare several kinds of H2SO4.
- Put some zinc or iron in it
- Find the speed of the reaction.
- Choose the best one for your Experiment
Part. B (The Device to catch H2)
- Mix 3mL detergent, 2 mL of glycerin, and 10 mL of pure water in a beaker. Then shake it a little bit.
- Take a silicone rubber tube (R=8mm, r=6mm), take 2cm of it. Then grasp it tightly on the pipette (about the 10mL string).
- Put the pipette in the liquid from step. 1 then take it till it reach the 2mL string.
- Put the zinc-iron nail into the test tube with acid inside. Quickly Tight the other head of the rubber tube on the test tube.
- Record the height of the bobbles reach.
Part. C (Check the zinc)
- Use the right length of the iron wire and nail.
- Make sure it’s surface.
- Guess the rate of zinc and iron.
- Make sure the weight is 0.0001g.
- Put the nail in acid and make it sink in the acid totally.
- Quickly fallow Part. B and get the Volume of H2.
- Wish the nail after step.6
- Use the wire to do it again
- Calculate the percent of zinc on the wire and nail. And get it’s thickness.
- Results:
|
Temp(oC) |
22 |
pressure(cmHg) |
76.11 |
MZn(g/mole) |
65.38 |
||
|
pressure of water(cmHg) |
1.9833 |
DZn(g/cm3) |
7.4 |
||||
|
1 |
2 |
3 |
4 |
||||
|
weight(B) |
2.9075 |
weight(B) |
2.8833 |
weight(B) |
2.9277 |
weight(B) |
2.9389 |
|
weight(A) |
2.9017 |
weight(A) |
2.8733 |
weight(A) |
2.9202 |
weight(A) |
2.9279 |
|
weight(Zn) |
0.0058 |
weight(Zn) |
0.01 |
weight(Zn) |
0.0075 |
weight(Zn) |
0.011 |
|
V(Zn) |
0.000784 |
V(Zn) |
0.001351 |
V(Zn) |
0.001014 |
V(Zn) |
0.001486 |
|
H2(mL) |
2.2 |
H2(mL) |
2.9 |
H2(mL) |
2 |
H2(mL) |
3.3 |
|
moles(Zn) |
9.58E-05 |
moles(Zn) |
0.000126 |
moles(Zn) |
8.71E-05 |
moles(Zn) |
0.000144 |
|
g(Zn) |
0.006263 |
g(Zn) |
0.008256 |
g(Zn) |
0.005694 |
g(Zn) |
0.009395 |
|
V(Zn) |
0.000846 |
V(Zn) |
0.001116 |
V(Zn) |
0.000769 |
V(Zn) |
0.00127 |
|
Surface(cm2) |
5.2056 |
Surface(cm2) |
5.2049 |
Surface(cm2) |
5.203 |
Surface(cm2) |
5.2034 |
|
Thickness(W) |
0.000151 |
Thickness(W) |
0.00026 |
Thickness(W) |
0.000195 |
Thickness(W) |
0.000286 |
|
Thickness(H2) |
0.000163 |
Thickness(H2) |
0.000214 |
Thickness(H2) |
0.000148 |
Thickness(H2) |
0.000244 |
|
Layers(W) |
3745.410529 |
Layers(W) |
6458.473 |
Layers(W) |
4845.623 |
Layers(W) |
7106.368 |
|
Layers (H2) |
4044.688195 |
Layers (H2) |
5332.351 |
Layers (H2) |
3678.827 |
Layers (H2) |
6069.597 |
|
Avg. Thickness from weight |
0.000223 |
Avg. Layers from weight |
5538.969 |
||||
|
Avg. Thickness from H2 |
0.000192 |
Avg. Layers from H2 |
4781.366 |
||||
PS: All the length is using cm
- Discussion:
When collecting H2, we found that it will be safer if we use our hand to hold the test tube. And use weak acid can be more accurate than using strong acid like H2SO4. About the results, we found that the first and the third nail is less Zn on it. And the second and the forth is about 1.5 times more. We think this is not a mistake. It’s because the amount of Zn on each nail will be different. Maybe these four nails are made in different time.
About the atomic packing structure of Zn, it is hexagonal close packing (六方最密堆積,HCP). So it look like this. And the r of Zn is 134 pm. the
We can find the cell’s height is 2 2 r (402pm).
- References:
Wikipedia:
http://en.wikipedia.org/wiki/Main_Page
李鈞震2013藝術文化讀書會:
http://earthkart2011.blogspot.tw/2013/07/structure-and-bonding-in-metals.html
- Reflection and Feedback:
We think we do this Experiment very successful cause the amount of Zn we get from different ways is close. Thought the Avg. Thickness from weight is more than the Avg. from H2.
留言列表
