CHEMISTRY - let the reactions react now .

On Friday, September 16, 2011 at 7:38 AM 1 comments ♥

Q1 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.


i) salt , ammonium nitrate , NH4NO3
base , zinc hydroxide , ZnOH
ii)white precipitate is produced .
iii)Zn(NO
3)2 [aq] + 2NH4OH [aq] → 2NH4NO3 [aq] + Zn(OH)2 [s]
iv)Zn2+ [aq] + 2OH- [aq] → Zn(OH)2 [s]

Q2 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.

i) (NH4)2SO4 [aq] + 2NaOH [aq] → Na2SO4 [aq] + 2NH3 [g] + 2H2O [l]
ii) place a damp red litmus paper at the top of the test tube , ammonia gas will turn red litmus paper blue .

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.
(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) nitrate ion
iii) iron(II) ions

Q4 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) they are soluble and colourless , titration method with an indicator can determine the end point of the neutralization between the acid and the alkaline . and group I salt is produced
ii) 2H+ [aq] + 2OH- [aq] → 2H2O [l]

Q5 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) ZnCO3 [s] + 2H+ [aq] → Zn2+ [aq] + CO2 [g] + H2O [l]
ii) excess zinc carbonate is added to ensure the acid is completely reacted
iii) add excess zinc carbonate to hydrochloric acid , filter all out excess zinc carbonate and boil the solution in a evaporating dish , control the fire to prevent salts from " jumping " out . let the solution to cool under a fan and zinc chloride crystal is formed .


credits :
http://www.answers.com/topic/anionic
http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA4/MVHTM/ZNNO/ZNNONH3X.HTM
http://www.blurtit.com/q8525847.html


On Thursday, July 7, 2011 at 12:54 AM 0 comments ♥

3 comments i made . :)

jiale's
his video is rather interesting , he presented his work clearly too . it's easy to read and understand .

aleen's
her drawings are clear and easy to understand . she added songs in her blog too . she added the credits too .

agnes's
her answers are easy to understand but it's a little lengthy and one of her picture couldn't fit into the post , maybe she can edit her picture a little smaller , so it can be seen clearly .


On Sunday, July 3, 2011 at 9:20 PM 0 comments ♥

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


atom is the smallest foundation unit or particle of an element that can exist . it looks like a circle with shells outside , each shell contains electrons and they lose or gain electrons to stability . the sub-atomic particles are protons , neutrons and electrons . the proton is a positive charge (+1) , the electron is a negative charge (-1) , neutron is neutral , 0 . the mass of a proton is the same as the mass of the neutron . the mass of the electron is much lighter than a proton and neutron . proton's relative mass is 1 , electron's relative mass is 1/1840 , neutron's relative mass is 1 .

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



sodium atom , ( 2.8.1 ) to gain stability , it needs to lose one electron on the outermost shell and causing it to become ( 2.8 ) , sodium ion .


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


sulfur atom , (2.8.6) to gain stability , it needs to gain 2 electrons , to lose 6 electrons , too much effort are needed , to gain 2 electrons is easier than losing it . therefore , it becomes , (2.8.8)

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


isotopes are different atoms of the same element which have the same number of protons but different number of neutrons .
chlorines have the same number of protons ( 17 protons ) , cl-35 have 18 neutrons , cl-37 have 20 neutrons . therefore , they are isotopes .


5. Sodium is a metal and sulfur is a non-metal. why we classify them this way?


sodium is na+ , positive charged , and it's in period I , therefore it is a metal .
sulfur is S2- , negatively charged , and it's in period VI , therefore it is a non metal .



On Monday, June 27, 2011 at 2:39 AM 0 comments ♥

trolols !

well , well , well .


bye !