Wednesday, September 9, 2009
|Color of Gold||Alloy Composition|
|Yellow Gold (22K)||Gold 91.67% |
|Red Gold (18K)||Gold 75% |
|Rose Gold (18K)||Gold 75% |
|Pink Gold (18K)||Gold 75% |
|White Gold (18K)||Gold 75% |
Platinum or Palladium 25%
|White Gold (18K)||Gold 75% |
|Gray-White Gold (18K)||Gold 75% |
|Soft Green Gold (18K)||Gold 75% |
|Light Green Gold (18K)||Gold 75% |
|Green Gold (18K)||Gold 75% |
|Deep Green Gold (18K)||Gold 75% |
|Blue-White or Blue Gold (18K)||Gold 75% |
|Purple Gold||Gold 80%|
Making Salts: Double Replacement Reactions and Ionic Compounds
In order for a double-replacement reaction to take place, ion has to encounter ion. This typically takes place in solutions. Furthermore, one of the products must be either a molecule, like water, or a gas or an insoluble salt. The following salts, which are found on the back of this sheet, are insoluble. This means that they do not dissolve in water. Your task is to choose to make one of these salts and to separate it in a pure form, using the solubility properties and double replacement reactions. Furthermore, each of the salts has a challenge associated with it. With the help of your instructor your group will choose a salt to make. (Only one group per salt.) A list of starting salts from which you can choose and make your own insoluble salt is at the top of the backside of this sheet. Over the course of the next week you will complete this project and hand in your report as a chemical journal article. (Sample journal articles are available in class for your perusal.)
In your Journal Article you will need to give an account of what you have done. This article will need to contain:
(a) an introductory paragraph in which you lay out your overall purpose, outline a basic procedure, and explain key concepts like a double replacement reaction. Be sure to be specific in your introduction about the salt you are making. Include specific chemical equation(s).
(b) a list your materials and equipment used.
(c) a step by step procedure so that someone else could repeat the lab you did.
(d) recorded measurements and observations. (Be sure to include any measured values, such as masses or volumes or times.)
(e) a explanation of how you met (or tried to meet) the challenge. Put this in a paragraph called “Meeting the Challenge.”
(f) a summary of your overall results within some concluding remarks.
Guidelines for Procedure:
Use small amounts of the salts (i.e. <>
Be careful not to contaminate the salt supplies; use what you need, put the top back on and return the salt container to the centralized tray.
Work in the smaller test tubes so that they will fit into the centrifuge.
When using the centrifuge be sure that it is always counterbalanced on the opposite side with a test tube of water of equal volume.
Record what you do as you do it. Don’t worry about back tracking and trying again.
Dispose of waste solutions and salts in an appropriate waste container as provided.
The next page contains the salts from which you can choose the one you would like. Discuss with your instructor which one would be right for your lab group to choose.
Sodium carbonate potassium hydroxide cobalt (II) chloride
Zinc sulfate nickel (II) sulfate nickel (II) chloride
Aluminum chloride magnesium sulfate calcium chloride
Copper (II) sulfate copper (II) chloride sodium hydroxide
SALTS TO MAKE – Choose one to make and meet the challenge.
1. Make: Nickel (II) carbonate
Challenge: Take the nickel carbonate, add HCl, interpret results
2. Make: Zinc carbonate
Challenge: After you have the zinc carbonate pure salt, find a way to dissolve it.
3. Make: Cobalt (II) hydroxide
Challenge: Prove to your instructor that all the cobalt ions you started with have been converted to cobalt hydroxide.
4. Make: Aluminum hydroxide
Challenge: Find a way to turn aluminum hydroxide into aluminum nitrate
5. Make: Magnesium carbonate
Challenge: Test pH of all solutions you used. Interpret results.
6. Make: Calcium sulfate
Challenge: End with a blue layer in your test tube
7. Make: Copper (II) hydroxide
Challenge: Gently heat the copper hydroxide using a bunsen burner.
Make a hypothesis as to the identity of the "new" salt formed.
Tuesday, July 21, 2009
Saturday, June 27, 2009
Albert Tay 59
Andy Malvine 65
Ang Fong Ying 82
Aurelia Tay 47
Beatrice Selester 54
Cecelia Simon 48
Charleston Chin 59
Christopher Primus 47
Cliff Rayner Azmi 48
Cynthia Hilarius 80
Esra Daniel 57
Eva Brenda Philip 38
Gerard Fung 76
Iresh Chia 71
Jessel Daniel 34
Jessie Daud 78
Kenneth Yong 62
Mohd Afiq Iqbal 78
Mohd Asraf Ruzaini 52
Natalie Chu 63
Nurul Suhaila Jamal 61
Ong Min Li 55
Sharizah Warno 59
Simon Chung 60
Stelly Lai 53
Vera Gan 61
What is electroplating?
Electroplating is the deposition of a metallic coating by putting a negative charge on an object and exposing it to a solution containing a metal salt. The positively charged metal ions in the salt solution are attracted to the object and reduced to metallic form upon it.
How does it work?
Look at the figure above: We have a metallic object we want to plate with a metal. First we fill a cell with a solution of a salt of the metal to be plated. Most of the time the salt (nickel chloride in our example) is simply dissolved in water and a little acid.
The NiCl2 salt ionizes in water into Ni++ ions and two parts of Cl- ions.
A wire is attached to the object, and the other end of the wire is attached to the negative pole of a battery (with the blue wire in this picture) and the object is immersed in the cell. A rod made of nickel is connected to the positive pole of the battery with the red wire and immersed in the cell.
Because the object to be plated is negatively charged (by being connected to the negative pole of the battery), it attracts the positively charged Ni++ ions. These Ni++ ions reach the object, and electrons flow from the object to the Ni++ ions. For each ion of Ni++, 2 electrons are required to neutralize its positive charge and 'reduce' it to a metallic atom of Ni0. Thus the amount of metal that electroplates is directly proportional to the number of electrons that the battery provides.
This relationship is a reflection of Faraday's Law of Electrolysis. If you are advanced enough in chemistry (a high school student), that you've heard terms like gram molecular weight, mole, valence and Avagadro's number, but it's all a hodepodge to you instead of a cohesive whole, don't despair! Study Faraday's Law, and suddenly all of these disparate wacky terms will come together in a moment of enlightenment.
Meanwhile back at the anode, electrons are being removed from the Nickel metal, oxidizing it to the Ni++ state. Thus the nickel anode metal dissolves as Ni++ into the solution, supplying replacement nickel for that which has been plated out, and we retain a solution of nickel chloride in the cell.
As long as the battery doesn't go dead, nickel continues to dissolve from the anode and plate out onto the cathode.
We used nickel chloride in the example chiefly for simplicity of explanation. First, because nickel always dissolves in the "+2" oxidation state (Ni++), whereas many other metals like copper and zinc can dissolve in either the "+1" or "+2" state and add some confusion; secondly because chloride is a simple one-atom anion whereas most anions like sulphate or acetate are far more complex. But we do not recommend that nickel be used for school science demonstrations because -- while the explaining is simple -- the plating is difficult :-)
For school demonstrations, we suggest plating copper pennies with zinc, or plating quarters or brass keys with copper.
Purification of copper
When copper is made from sulphide ores by the first method above, it is impure. The blister copper is first treated to remove any remaining sulphur (trapped as bubbles of sulphur dioxide in the copper - hence "blister copper") and then cast into anodes for refining using electrolysis.
The purification uses an electrolyte of copper(II) sulphate solution, impure copper anodes, and strips of high purity copper for the cathodes.
The diagram shows a very simplified view of a cell.
At the cathode, copper(II) ions are deposited as copper.
At the anode, copper goes into solution as copper(II) ions.
For every copper ion that is deposited at the cathode, in principle another one goes into solution at the anode. The concentration of the solution should stay the same.
All that happens is that there is a transfer of copper from the anode to the cathode. The cathode gets bigger as more and more pure copper is deposited; the anode gradually disappears.
In practice, it isn't quite as simple as that because of the impurities involved.
What happens to the impurities?
Any metal in the impure anode which is below copper in the electrochemical series (reactivity series) doesn't go into solution as ions. It stays as a metal and falls to the bottom of the cell as an "anode sludge" together with any unreactive material left over from the ore. The anode sludge will contain valuable metals such as silver and gold.
Metals above copper in the electrochemical series (like zinc) will form ions at the anode and go into solution. However, they won't get discharged at the cathode provided their concentration doesn't get too high.
The concentration of ions like zinc will increase with time, and the concentration of the copper(II) ions in the solution will fall. For every zinc ion going into solution there will obviously be one fewer copper ion formed. (See the next note if you aren't sure about this.)
The copper(II) sulphate solution has to be continuously purified to make up for this.
Monday, June 15, 2009
In this topic, you'll have to be able to learn about electrolytes, half equation, factors affecting electrolysis (Electrochemiscal Series, Type of electrode and Concentration of electrolyte), electrolysis in industry (electroplating, extraction, purification), voltaic cell....
Electrochemical Series (ES) for positive ions
ES for negative ions
Monday, May 18, 2009
Monday, April 27, 2009
Monday, April 13, 2009
Here is some information on paper 2 = 100marks = 50%
This is the part where questions can be quite challenging because structure questions are often mixed with higher order thinking questions. The good news is, since its only on 4 topics.. it's not very difficult... U can do it!!!
Structure 1 to 6 = 10marks X 6 = 60marks
(two questions from chapter 2, two from chapter 3, one from chapter 4 &
two from chp5)
To score an A, its advisable to get about 6marks from each questions....
[36marks = 18%]
To pass? U need at least 4marks from each questions....[24marks = 12%]
Two essay questions... (Chapter 2 & 3)...choose ONE only...[20 marks = 10%]
try to get at least 10 marks...[5%]
Two essay questions as well...(Chapter 4 & 5)... choose ONE only...
.... a total of [40 marks = 20%] will be needed to pass....
.... a total of [66 marks = 33%] for those who wants to score...
Wednesday, April 8, 2009
question number 1 and 2 is usually related to reading an apparatus reading, variables or graph, practically will be only about experiments... so read up on all the possible experiments from now on...
List of Experiments:
1. Heating and cooling of napthalene
2. Determining emperical formula for Magnesium oxide (reactive metals)
3. Determining emperical formula for copper oxide (less reactive metals)
4. Group 1 - reaction with Chlorine..Oxygen..Water..
5. Group 17
6. Period 3
(a few simple experiments from chapter 5)
You can discuss anything here regarding those experiments... pls share info here..
An ionic bond is the force of attraction between the opposite charges of an ion. One element in an ionic bond loses electrons, and another element must gain the electrons. Some atoms lose electrons to make the outside energy levels become more stable. Atoms become more stable when their outer most energy level has 8 electrons. Pure ionic compounds usually are crystalline solids, liquids, or gases.
1.Ionic bonding occurs when ions of ________ carge are attracted to one another.
A. opposite B. positive C. negative D. equal
2.Which substance is an Ionic bond?
A. CO B. CaCl2 C. CO2 D. Al
I've set the questions for you.
12 questions from chapter 2: mostly about nucleon no, proton no, nuetron no, electron configuration, heating and cooling of napthalene...
13 from chapter 3: lots of calculations, be ready in term of how to calculate the number of particles, number of molecules, moles, empirical formula, molecular formula...
12 from chapter 4: quite easy except for the equations... watch out for it!!
and 13 from chapter 5: hehe, here, its all about compounds, both ionic and covalent compound.. quite easy!
Tuesday, March 17, 2009
Lithium is a Group 1 element containing just a single valence electron. Group 1 elements are called "alkali metals". Lithium is a solid only about half as dense as water and lithium metal is the least dense metal. A freshly cut chunk of lithium is silvery, but tarnishes in a minute or so in air to give a grey surface. Its chemistry is dominated by its tendency to lose an electron to form Li+. It is the first element within the second period. Lithium is mixed (alloyed) with aluminium and magnesium for light-weight alloys, and is also used in batteries, some greases, some glasses, and in medicine.
Potassium is never found free in nature, but is obtained by electrolysis of the chloride or hydroxide, much in the same manner as prepared by Davy. It is one of the most reactive and electropositive of metals and, apart from lithium, it is the least dense known metal. It is soft and easily cut with a knife. It is silvery in appearance immediately after a fresh surface is exposed. It oxidises very rapidly in air and must be stored under argon or under a suitable mineral oil. As do all the other metals of the alkali group, it decomposes in water with the evolution of hydrogen. It usually catches fire during the reaction with water. Potassium and its salts impart a lilac colour to flames.
Thursday, March 12, 2009
sleep? TV? games? visiting?.... U still need to allocate time to revise n homework....
u can still relax but dun forget to spend sufficient time on ur studies...
in science stream, this is a sacrifice u need to do... pls work this out in ur mind...
if u think u can play this year... then u r making a terrible mistake!
This reminds me of our school's SPM result which was out today....
Chemistry huh..... 8 students got A and 17 students got B and the rest got C....
Can you beat this result or at least maintain it?...
so, do the "SKOR A" questions i gave u guys to complete ya hehehe...
Sunday, March 1, 2009
January and February must have been very challenging months for all of you as u learnt so many new things, new studying culture, loads of homework, pressure, and high expectations from ur parents n etc...
Chemistry, we've covered 2 chapters which are the basics for upcoming topics. If u have any problems in any part of it, feel free to ask here. If u r already good, then keep up ur good work!!! I will be posting ur chemistry test result here... hehehe (devilsh laughter)... so, it will be a learning platform for all of u. Just don't be too tensed up.. relax but not too much.. take a deep breath... then proceed back to focus! all da best.. welcOme MARCH!!!!!! :D
Friday, February 20, 2009
Thursday February 19, 2009
Tuesday, February 17, 2009
e.g. When 4g of Magnesium reacts in oxygen gas, magnesium oxide will be produced. Calculate the mass of magnesium oxide produced?
Firstly, you have to write out the equation....
Mg + O2 --> MgO
Next, check if the equation is balanced or not... Looks like it is not balance.. so, BALANCE it now!
you should get...
2Mg + O2 --> 2MgO
Now we can start our calculation... given is 4g of magnesium... so we need to calculate the mole value for Magnesium...
Mole = Mass / RAM or RMM
mole = 4g/24 and you'll get 0.1667 mole
Now you have to refer to your balanced equation...
2 mole of Magnesium will produce 2 mole of Magnesium Oxide
therefore, 0.1667 mole of Mg will also produce 0.1667 mole of MgO
The final step now is to convert the mole value of MgO to mass...
mole = mass / RAM or RMM
Mass= mole X RAM or RMM
= 0.1667 X [24 + 16]
= 0.1667 X 40
** leave your answer in 2 decimal places...
Q: What is the mass of copper oxide that will be needed to produce copper when it is reacted with hydrogen gas?
[Cu=64, H=1, O=16]
Balancing a chemical equation is a very important knowledge in chemistry. What u need to do when u have to balance a chemical equation?
e.g. Al + CuO --> Al2O3 + Cu
Now the equation is not balanced.. Firstly U have to know how many Al atoms are on your left? Only 1 but you have 2 Al atoms on your right.. so u put a no 2 infront of Al...
2Al + CuO --> Al2O3 + Cu
Now u find that the number of oxygen isn't balance.. so you'll have to do something.. you can add the no 3 to CuO so that you have 3 oxygen atoms...
2Al + 3CuO --> Al2O3 + Cu
Problem now is... you have 3 Cu atoms on your left but only 1 Cu atom on your right... to make it balance, you can add the no 3 to Cu...
2Al + 3CuO --> Al2O3 + 3Cu
Now you hae a balanced equation... It is not that difficult right... try this and tell me your answer:
a) H2 + O2 --> H2O
b) Fe + Cl2 --> FeCl3
c) KMnO4 + HCl --> KCl + MnCl2 + H2O + Cl2
Good Luck :D
Saturday, February 14, 2009
I hope u gained something & learnt something 4rm the trip besides beaches, 1B and etc.. I, myself learnt a lot.. never seen so many things when I was in school or University.. U all r so gifted hehe... I hope U'l had benefited fr this trip.. Tq foe behaving well tru out the trip.. Cheers!!!
Friday, February 6, 2009
Tuesday, February 3, 2009
What Happens When Bleach and Vinegar Are Mixed
Chlorine bleach contains sodium hypochlorite or NaOCl. Because bleach is sodium hypochlorite in water, the sodium hypochlorite in bleach actually exists as hypochlorous acid:
NaOCl + H2O ↔ HOCl + Na+ + OH-
Hypochlorous acid is a strong oxidizer. This is what makes it so good at bleaching and disinfection. If you mix bleach with an acid, chlorine gas will be produced. For example, if you mix bleach with toilet bowl cleaner, which contains hydrochloric acid:
HOCl + HCl ↔ H2O + Cl2
Chlorine gas attacks mucous membranes, such as your eyes, throat, and lungs and can kill you, so causing that reaction isn't in your best interest. If you mix bleach with another acid, such as the acetic acid found in vinegar, you get essentially the same result:
2HOCl + 2HAc ↔ Cl2 + 2H2O + 2Ac- (Ac : CH3COO)
There is an equilibrium between the chlorine species that is influenced by pH. When the pH is lowered, as by adding toilet bowl cleaner or vinegar, the ratio of chlorine gas in increased. When the pH is raised, the ratio of hypochlorite ion is increased. Hypochlorite ion is a less efficient oxidizer than hypochlorous acid, so some people will intentionally lower the pH of bleach to increase the oxidizing power of the chemical, even though chlorine gas is produced as a result.
What You Should Do Instead
Don't poison yourself! Rather than increasing the activity of the bleach by adding vinegar to it, just buy fresh bleach! Chlorine bleach has a shelf life. This is particularly true if your bleach has been hanging around for several months. It's far safer for you to buy fresh bleach than to risk releasing a chemical weapon on yourself by mixing bleach with another chemical. You can use bleach and vinegar for cleaning, just make sure you rinse before switching products!!!
Friday, January 30, 2009
Wow, I wonder how many % of oxygen is produced by Sabah's forest??!
The noble gas Xenon lasers can cut through materials that are so tough even diamond tipped blades will not cut.
Diamond is the hardest element man.. amazing huh..
Gold and Copper are the only two non-white metals.
The burning sensation we get from chilli peppers is because of a chemical called Capsaicin.
hmmm... so this capsaicin is detected by all our taste buds ka?
The lighter was invented before the match (in 1816 by J.W. Dobereiner).
huh? Really.. so y v still need match when v have lighter???
Each time lightning strikes, some Ozone gas is produced, thus strengthening the Ozone Layer in the Earth's atmosphere.
God... send some lightning & thunder...
Honey does not spoil.
God's creation... x expiry date... wonderful...
There's enough gold in the Earth's crust to cover the entire land surface knee-deep.
I wonder where's all the gold now hahaha....
An average adult body contains around 250g (1/2lb) of salt.
ewwww... that's a lot!!!
Thursday, January 22, 2009
Wednesday, January 21, 2009
Number of particles= mole X Avogadro Constant
(remember, number of atoms, ions and molecules must be identified as the calculation varies)
Example, Number of particles for 1 mole of H2 is 6.02 X 1023 molecules BUT Number of atoms will be 2 X 6.02 X 1023 ( one hydrogen molecule has 2 hydrogen atoms!)
Mass of a substance = Mole X Molar Mass
(Molar mass is calculated as RAM or RMM BUT the Unit is g per mol)
Volume of Gas = Mole X Molar Volume
(For STP, molar volume is 22.4 whereas, for room conditions, molar volume is 24)
X NA X Molar Mass
number of particles ----> mole ----> mass
l X Molar Volume
Volume of gas
Notes: 1 dm3 = 1000 cm3
Wednesday, January 14, 2009
Teacher Donny & I had planned a Trip for all of u to KK on February 12-13.
We will be visiting Electroplating & Aluminium Factory, Milk processing Factory,
Formaldehide Factory, and also Noodle factory.. all these r kind of related to your chemistry, physics and biology... accompanying teachers will be Mr. Robert, Mr. Donny, Madam Norhafiza & myself. you'll need to pay RM50 for this trip. We'll be staying at SaBah Kinabalu Hostels, Likas. Please spread the news.. formal letter will be given out soon.. probably by next week ya
1. Kinetic theory of gas & matter (solid, liquid & gas)
2. Heating & Cooling graph
3. Nucleon No, Proton No & Neutron No
4. Electron arrangement/ electron configuration of an element
Any problem understanding these subtopics? Post ur opinion here. U can write
down tips n discuss ur problem....