Comments:

Aleen

Her answers are well-written and reader-friendly. She provides accurate and informative answers. However, for question 4ii) and 5i), the question is asking for the ionic equations, but both her answers are in chemical equations.

Yihui

Her answers are short and straightfoward. For question 1, zinc hydroxide , ZnOH should be Zn(OH)2. For question 5, it would be better in she includes "add until there is excess solid" so that it's able to filtrate.

ChunBoon

His answers are excellent. I would prefer him putting Zn2+ instead of Zn(+). To make his life more easier, he can write on a piece of paper and post it. And also, he made a slight mistake in question 1 iv), it should be Zn2+ instead of Zn(+). For question 3iii), it is supposed to be Iron (II) ion instead of Iron (III) ion which gives the green soluion.

Overall, everyone's answers are great. I can see them putting in effort in providing quality answers ^o^

Question 5: Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.

(i) Write an ionic equation for the reaction.

(ii) Why excess zinc carbonate is used?

(iii) Briefly explain how the zinc chloride crystals can be obtained.

(i)

(ii) To ensure that zinc carbonate is completely reacted with hydrochloric acid.

(iii) By adding zinc carbonate to the hydrochloric acid until there's excess solid left. Filter to remove excess unreacted zinc carbonate. Heat the filtrate until it's left with some water for crystallisation.

Question 4: Sulfuric acid is titrated with potassium hydroxide in the preparation of potassium sulfate salt.

(i) Explain why this method is recommended for the preparation for this salt.

(ii) Write an ionic equation for the reaction.

(i) Potassium sulfate is a Group I salt, which is soluble. Since both solutions are colourless, we can used titration method and an indicator to determine the end-point of neutralisation between the two solutions.

(ii)

Question 3: 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.

(ii) This is a confirmatory test for an anion. Name this anion.

(iii) Give a possible cation which gives the green solution.

(i) Ammonia gas

(ii) Nitrates

(iii) Iron (II) ion

Question 2: Ammonium sulfate is heated with sodium hydroxide.

(i) Write a chemical equation (include state symbols) for the reaction.

(ii) Describe a test for the gas.

Question 1: Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base.

(i) Name the salt and the base.

(ii) Describe the observations for the reaction.

(iii) Write a chemical equation for the reaction (include state symbols). (iv) Write an ionic equation for the reaction.

Aleen (27)
Her answers are very detailed and informative. She also provided a lot of pictures for better understanding. It was very useful for her to put the list of topics we learnt on her blog. She once put 'S' for Sodium atom instead of 'Na', I told her about that and she changed her answers immediately, which shows her concern for her answers. I think it would be better if she summarise her answers or else it would be too lengthy.

Yihui (22)
Blog design is simple yet nice. The pictures of the drawings are kind of blur. From question 3 to 5 onwards, she should increase the size of her fonts, the words are just too small for anyone too read. Also for question 5, she should also state the phyiscal properties of the classification of metals.

Clarence (32)
His blog is quite well done esp the design. The electron's mass is 1/1840 instead of 1/1836 according to the textbook (He has changed it). I can't seem to see the picture for question 1, he should change the picture or remove it. I liked the way he answered question 5, because other than saying the chemical/physical properties, he said that the metals, transition metals and non-metals from which group. That's also another way of classifying them. He also gave the definition of Isotopes even though the question didn't require it.


-----------------------------CAN BE IGNORED :/ ----------------------------------------
JunWei (38)
Once I entered his blog, I saw snail and bee flying around. And that '`FLYWITHYOUUU' seems to distract me a lot. It would be better if he changed it to '`FLYWITHMEEE' sounds more original. When I scrolled right, I even saw a dog ! 妈呀, he 14 years old or 4 years old? He should find a blogskin more suitable for his age. Other than that, his information provided are pretty useful and understanding.

CNY'2011 outing with 2E5'10 <3

Seoul Garden ! :>

Vietnam trip'09 with 2E5'10 awesome people \m/

Best picture must always be saved for the last ;)

Look at Oh Jun Wei, he looked like some kind of uncle. The rest of them looked like small kids ><

http://www.youtube.com/watch?v=T6UujimddEc&feature=player_embedded

ENJOY ~ !

#1 What does an atom looks like? What are the sub-atomic particles inside it.....(talk about electrons, neutrons, protons, electron shells, nucleus....)

An atom looks like a nucleus surrounded by an orbital electron shell.
An atom consists of sub-atomic particles such as:

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Protons

-carries one positive electric charge (+1)

-has a relative mass of 1

-is represented by the symbol, p

Neutrons

-carries no electric charge

-has a relative mass of 1

-is represented by the symbol, n

Electrons

-carries one negative electric charge (-1)

-has a relative mass of 1/1840 (negligible)

-is represented by a symbol, e

-------------------------------------------------------------------------------------------

These particles are even smaller than the atoms themselves. They are called sub-atomic particles.

The protons and neutrons are found in the nucleus of the atom. These two particles that make up the nucleus are known as nucleons.

Electrons move rapidly around the nucleus in definite energy levels or electron shells.

http://www.antonine-education.co.uk/physics_as/module_1/topic_1/Atom_1.gif

#2 Draw the atomic structure of a sodium atom and a sodium ion....explain why you draw it this way.

The sodium atom is drawn this way as its electronic configuration is (2.8.1) only having one electron on its last shell. The sodium ion however is stable and has lost its one electron on the outermost shell causing its electronic configuration to be (2.8) only.

#3 Draw the atomic structure of a sulfur atom and a sulfide ion....explain why you draw it this way.

The sulfur atom is drawn this way as its electronic configuration is (2.8.6) having six electrons on its last shell. The sulfur ion however is stable and has gained 2 electrons on the outermost shell causing its electronic configuration to be (2.8.8).

#4 Chlorine-35 atom and Chlorine-37 atom are called isotopes...Use these two examples to explain what is 'isotopes'.

Chlorine-35 has 35 as its nucleon number. Therefore, (35-17=18) it has 17 protons and 18 neutrons

Chlorine-37 has 37 as its nucleon number. Therefore, (37-17=20) it has 17 protons and 20 neutrons.

Isotopes are different atoms of the same element which have the same number of protons but different number of neutrons.
Chlorine in this case has 18 and 20 neutrons respectively. As chlorine has two different number of neutrons but same number of protons, thus, they are called isotopes.

http://alexteoh.com/Atomic%20Structure.htm

#5 Sodium is a metal and sulfur is a non-metal....why we classify them this way??
Physical properties
Metal conduct electricity well while non-metal is a poor conductor of electricity

Chemical properties
Sodium (2.8.1) is a metal because it will lose 1 electron to complete the valence shell.
Sulfur (2.8.6) is a non-metal because it will gain 2 electrons to complete the valence shell

Okay, Chemistry blog created.