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HEYY everyone
this is Su here. ;)
this is practically all about chem here. see how it progress. in any case, pardon me.i know my blog sucks :)
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Friday, 23 September 2011
Qs and As on Ionic Equations, Colours of Cations & Anions, Acids, Bases, Alkalis, Salts @ 05:53
Q1) Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base.
Zinc nitrate + aqueous ammonia ---> Ammonium nitrate + Zinc hydroxide
(i) Name the salt and the base.
The salt is Ammonium nitrate, NH4NO3
The base is Zinc hydroxide, Zn(OH)2
(ii) Describe the observations for the reaction.
A white precipitate (Zinc hydroxide) is formed when Zinc nitrate solution is added to aqueous Ammonia solution.
(iii) Write a chemical equation for the reaction (include state symbols).
Zn(NO3)2 (aq) + NH3 (aq) --> NH4NO3 (aq) + Zn(OH)2 (s)
(iv) Write an ionic equation for the reaction.
Ionic Equation: Zn2+
(aq) + 2OH- (aq) --> Zn(OH)2 (s)
............................................................................................
Q2. Ammonium sulfate is heated with sodium hydroxide.
Ammonium sulfate + Sodium hydroxide --> Sodium sulphate + water + ammonia
(i) Write a chemical equation (include state symbols) for the reaction.
(NH4)2SO4 (aq) + 2NaOH
(aq) --> Na2SO4 (aq) + 2H2O (l) + 2NH3
(g)
(ii) Describe a test for the gas.
Use a damp red litmus paper. If it turns blue, it's ammonia gas.
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Q3. An unknown green solution is heated with a piece of aluminium foil and sodium hydroxide solution.
(i) The gas produced turns damp red litmus paper blue. Name the gas evolved.
The gas evolved is Ammonia gas.
(ii) This is a confirmatory test for an anion. Name this anion.
This anion is nitrate, NO−
3
3
(iii) Give a possible cation which gives the green solution.
Iron (III) ion.
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Q4. Sulfuric acid is titrated with potassium hydroxide in the preparation of potassium sulfate salt.
Sulfuric acid + Potassium hydroxide --> Potassium sulfate + water
(i) Explain why this method is recommended for the preparation for this salt.
Firstly, Potassium Sulfate is a Group(1) salt. Group(1) salts are all colourless soluble solutions, and thus, titration is require to determine the end-point of the neutralization between the acid and the alkali in preparation for this salt.
(ii) Write an ionic equation for the reaction.
H+2 (aq) + 2OH- (aq) --> 2H2O (l)
............................................................................................
Q5. Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.
Zinc carbonate + Hydrochloric acid --> Zinc chloride + water + carbon dioxide
(i) Write an ionic equation for the reaction.
ZnCO3 (s) + 2H+ (aq) --> Zn2+ (aq) +
H2O (l) + CO2 (g)
(ii) Why excess zinc carbonate is used?
This is to ensure that all the Zinc Carbonate is completely reacted with the Hydrochloric acid to form Zinc Chloride. When there is excess black copper (II) oxide seen, I know that the reaction has stopped.
(iii) Briefly explain how the zinc chloride crystals can be obtained.
The
Zinc Chloride formed is dissolved in water to obtain the
solid crystals. Heat the Zinc Chloride solution until a saturated solution is achieved. By allowing the solution to
cool down, we can obtain the Zinc Chloride crystals.
............................The End :) ...............................
Friday, 8 July 2011
Comments @ 05:57
Before reading the comments below, please take note that I mean no offence against anyone. I will just comment on what I feel about your blog and things that is on my mind related to this. But, I will try not to offend anyone in any bad way. Pardon me if I do comment things that you may dislike. No hard feelings please. Thank you.
Ysabelle : As for your answers to the questions, it is really informative and interesting. I'd like to suggest you to be more specific in terms of explanation and reasoning, as in words such as "kinda" should likely be excluded since one has to take a stand on the elaboration that he/she gives. In conclusion, all-in-all, the answers were rather inspiring.
Cindy : Your answers are more specific and with more of chemical terms, which was really different from many other answers I has came across. Well done fri. By the way, add some photos of you please.
Grace : Your explanation was simple, easy to understand and straight to the point. One suggestion that I'd make is to enlarge your font size and add more contrast to the background, because it is quite hard to read.
Shu Yu : Goodness.. It's quite a cute blog you have there! Nice photos too. Also, you have a lot of information provided for the answers. As for you, I suggest that you should enlarge your font so that it's easier to read.
Ei Ei : It's definitely a very decorative blog. Plus, the music is soothing too. The context is well provided. If possible, please occupy a larger column in terms of width for posts to have more space.
Xue Li : You have a very pretty blog. I love the background and photos(not to mention, it's super cool). But I feel that you should add the links from internet for copyright purpose, just as Mr Tan says.
Chelsea : Firstly, your blog is simple and nice-looking. You have given your answers in subtitles and I think it's really brilliant. It's really easy to read, as all the words are not cramped up in a small space. I think you should provide more information on the answers, to secure your marks.
Xin Hui : I'm sure it takes you much effort to choose that blog skin. It's really appropiate as it is only meant for chemistry and you had make a brillaint choice, I must say. I feel that there is quite little information in terms of context for the answers. I think you should add in a bit more. Great photos, by the way.
Ziqing: Your answers are very informative and it's fabulous. I'd like to comment on the font size, it's rather small but considered to some other blogs, I'm sure it's way better. Also, please add some photos if possible.
Hwee Leng : Your blog is so cool, especially the cbox. Nice photos, also. But, please enlarge the font size as it could minimise the reader's attention.
Shin Yoong : Colourful blog! and Cool photos. The drawings are a bit blur but nevermind that. I understand that photos can sometimes be much of a nuisance. Overall, it has great answers.
Tuesday, 5 July 2011
Photos! XD @ 06:19
Family :)
School Photo! (:
PEACE VV
Zoom in for the sticky note! 8)
Gateway to Harry Potter World..not :D
Friday, 1 July 2011
Atomic Structure Assignment @ 03:13
Mr Tan: Hi tcher..u know..i even went to the extent of taking photos of my drawings bcos I just couldn't directly paste it in my post. i put in sooo much effort for this :D MUST give me high marks tcher.thank you and please be sure to give me a longg comment. Thanks again. :D
1) What does an atom looks like? What are the sub-atomic particles inside it.....(talk about electrons, neutrons, protons, electron shells, nucleus....)
1) What does an atom looks like? What are the sub-atomic particles inside it.....(talk about electrons, neutrons, protons, electron shells, nucleus....)
Atoms are made up of three different particles – protons, neutrons and electrons. These particles are known as sub-atomic particles.
For example, the diagram on the left shows the atomic structure of a Helium atom that contains two protons, two neutrons and two electrons. Inside the nucleus of the atom, proton and neutron exist. Proton (p) has a relative charge of (+1) and relative mass of 1. Neutron (n) has a relative charge of 0 and relative mass of 1. The particle outside the nuclues is called electron. Its symbol is e and it has a relative charge of (-1) and relative mass of 1/1840. All atoms are neutral. Each atom contains equal number of positively charged protons and negatively charged electrons. Neutrons have zero charge.
The proton number (atomic number) is the number of protons in an atom. The nucleon number (mass number) is the number of protons and neutrons in the nucleus of the atom. The valence shell (outermost shell) is the shell which is furthest from the nucleus. The valence electrons are the electrons in the outermost shell of an atom. If the valence shell is full, the atom is stable or unreactive with other atoms. By gaining or losing electrons, atoms gain stability. Atoms that gain electrons are namely negative ions and atoms that gives out electrons are postive ions. Electronic configuration of each atoms tells us the arrangement of electrons in the various shells of an atom of molecule.
2) Draw the atomic structure of a sodium atom and a sodium ion....explain why you draw it this way.
3) Draw the atomic structure of a sulfur atom and a sulfide ion....explain why you draw it this way.
4) Chlorine-35 atom and Chlorine-37 atom are called isotopes...Use these two examples to explain what is 'isotopes'.
Conclusion:
5) Sodium is a metal and sulfur is a non-metal....why we classify them this way??
Atoms of metals tend to lose valence electrons to form positive ions or cations. Sodium atom loses an electron to form a Sodium ion, Na+, a cation, hence, it is a metal.
Atoms of non-metals tend to gaiin electrons to form negative ions or anions.
Sulphur atom gains 2 electrons to form a Sulphur ion, S2–, an anion, hence, it is a non-metal.
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