Q5 Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.

i) Write an ionic equation for the reaction.

 

 ZnCO3 (s) + 2H+ (aq) --> Zn 2+ (aq) + H2O (l) + CO2 (g)

ii) Why excess zinc carbonate is used?

 

Is to ensure that all the hydrochloric acid is completely reacted, before filtering the excess unreacted zinc carbonate from the zinc chloride solution.

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

Step 1: Add the excess zinc carbonate to a beaker of hydrochloric acid until there is excess zinc carbonate seen.

Step 2: Filter to remove the excess unreacted zinc carbonate.

Step 3: Evaporate the zinc chloride solution to remove the water and to obtain a saturated salt solution (heat slowly to prevent salt to jump out)

Step 4: Leave the hot saturated solution to cool down. When the hot saturated salt solution cools down, zinc chloride crystals is obtained.

 

 

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.

Potassium sulfate is a group (I) salt, colourless and soluble. Titration method is for group (I) and ammonium salt. Therefore, the salt can be prepared using titration method

ii)Write an ionic equation for the reaction.

2H+ (aq) + OH- (aq) à H2O

Q3 An unknown green solution is heated with a piece of aluminum foil and sodium hydroxide solution.

(i) The gas produced turns damp red litmus paper blue.  Name the gas evolved


Its ammonia gas


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


The anion is nitrate ion (NO3 -)


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

Q2 Ammonium sulfate is heated with sodium hydroxide.

(ii)  Describe a test for the gas

Hold a piece of damp red litmus paper over the mouth of the test tube. When the damp red litmus paper turns blue, it mean that ammonia gas is produce.

Q2 Ammonium sulfate is heated with sodium hydroxide

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

•(NH4)2 SO4 (aq) + 2NaOH (aq) --> Na2 SO4 (aq) + 2H2O (l) + 2NH3 (g)

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

(iv) Write an ionic equation for the reaction.  

 Zn 2+ (aq) + 2OH - (aq) -> Zn(OH)2 (s)

Q1 Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base.

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

 Zn(NO3)2 (aq) + 2NH4OH (aq) --> 2NH4NO3 (aq) + Zn(OH)2 (s)

Q1 Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base.

(ii) Describe the observations for the reaction

When zinc nitrate solution reacts with ammonium hydroxide (both colourless), a white precipitate of zinc hydroxide is will be produced .

Q1 Zinc nitrate reacts with aqueous ammonia (NH4OH) to form a salt and a base

(i) Name the salt and the base.

Salt is ammonium nitrate. Base is zinc hydroxide.

Comment 3

Kaiqi-
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Comment 2

Aleen :

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Comment 1

Ysabelle-

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

http://www.elementsdatabase.com/Images/periodic_table.gif






http://www.chemglobe.org/ptoe/periodic.png



Sulfur is a non-metal because:

1. it does not conduct electricity

2. it will gain electrons to complete the valence shell

3. it lies on top of the stair case on the table


Sodium is a metal because:

1. it conducts electricity

2. it will lose electron to complete the valence shell

3. it lies below the staircase (group1 )

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

Isotopes are atoms of the same element that have different nucleon number (mass no.) or different number of neutrons.
Isotopes  of the same element have similar chemical properties but different physical properties.

Since Chlorine-35 and Chlorine-37 have the same number of proton and  electron but different number of neutron, they are called isotopes of chlorine. Thus, the average nucleon number of chlorine will be  [(75/100) x35 ] + [(25/100) x37] =  35.5

Chlorine Atoms	No. of Proton	No. of Electron	No. of Neutron
Chlorine-35	17	17	18
Chlorine-37	17	17	20

http://alexteoh.com/Atomic%20Structure_files/image003.jpg


http://www.wordwizz.com/images/isotopes.gif

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

http://www.micromountain.com/sci_diagrams/at_struct/at_struct_assets/sulphur_lab_usa.jpg

Extra^^
http://www.webelements.com/_media/elements/kossel_diagrams/S.jpg


http://chemwiki.ucdavis.edu/@api/deki/files/4996/=Sulfate%20pt.%202.jpg




http://0.0.0.3/4.bp.blogspot.com/-Yy6H9WZQsK0/ThFsS_xMXJI/AAAAAAAAAEQ/bB0e3S_VoqU/s1600/Untitled-4jpg.jpg


Ionic bonds are formed when metallic atoms has given away their valence electrons to the non-metallic atoms.
The transfer of valence electrons from the metallic to the non-metallic atoms enables both atoms to achieve stablility.  (stable noble gas configuration)
oppositely charges ions are formed which will attacted to each other due to the strong electrostatic forces of attraction, that form the ionic bonds.

THerefore,  i drew the sulfur atom that way as its has 16 electrons .
 Its electronic configuration is (2.8.6). It need 2 extra valence electrons to become stable . Thus,sulfide  ion is drawn  that way because it has gained 2 valence electron . Hence, its electronic configuration has become ( 2.8.8 ) after recieving two electron. and is now negatively charge

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

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlF5vDL1_N-xq7plD6YADEOqZOn_0TwwOtFxNJxPzEmLsDj3I4-_kYVwdvngGZucfOZqdmlKdG5bBE1LQJAApqhVWY4ArXLh5slCDMKGu7b7EGWibg32m_mtGmQnGbWEeSoWQ6OXjxG47c/s320/Sodium-Atom-Sodium-Ion.gif




http://iss.cet.edu/electricity/pages/images/b/b11_5.jpg


Ionic bonds are formed when metallic atoms has given away their valence electrons to the non-metallic atoms.
The transfer of valence electrons from the metallic to the non-metallic atoms enables both atoms to achieve stablility.  (stable noble gas configuration)
oppositely charges ions are formed which will attacted to each other due to the strong electrostatic forces of attraction, that form the ionic bonds.

THerefore,  i drew the sodium atom that way as its has 11 electrons .

http://www.google.com.sg/imgres?imgurl=http://www.scioly.org/w/images/1/1b/Electron_shell_011_Sodium.svg.png&imgrefurl=http://www.scioly.org/wiki/GMOA_Notes&usg=__BWr41JgSP1sAjIKSHoywbKX933Q=&h=194&w=180&sz=10&hl=en&start=14&zoom=1&itbs=1&tbnid=M0tsb3vKAyYmyM:&tbnh=103&tbnw=96&prev=/images%3Fq%3Dthe%2Batomic%2Bstructure%2Bof%2Ba%2Bsodium%2Batom%2Band%2Ba%2Bsodium%2Bion.%26hl%3Den%26gbv%3D2%26biw%3D1003%26bih%3D622%26tbm%3Disch&ei=w7MZTqOSLsXVrQfGzPzPAQ


 Its electronic configuration is (2.8.1). It has 1 extra valence electron. thus, sodium ion is drawn  that way because it has given away it in order to become stable . Hence, its electronic configuration has become ( 2.8 ) after that removal of that electron. and is now positely charge

        


http://www.gcsescience.com/sodium-ion.gif

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 basic particles (sub-atomic ): protons, neutrons and electrons.

The properties of the three particles are shown in the table below:

Sub-atomic Particles	Relative Mass
Electron	1 / 1840
Proton	1
Neutron	1

The structure of an atom:





THe composition of protons, neutrons and electrons in an atom can be determined from its proton number ( atomic number)and nucleon number (mass number).
The proton number is defined as the number of protons in an atom.
The nucleon number is defined as the total number of protons and neutrons in the atom.
Since an atom is electronically neutal, number of protons should be equal to number of electrons in the atoms.
An atom cann be written with a symbol. Example:




MEANING:

1. The atom is sodium
2.Has 11 protons and electrons
3.Nucleon(mass)number of 23 (neutrons+ protons)
4. Has(23-11=) 12 neutrons

The way in which electrons are arranged in an atom among the various energy shells is called its electron configuration.
Each shell cann only hold up to a certain number of electrons
And each shell must be completely filled before going to the next level.
Examples:





Note that:

Protons and Neutrons are found in the nucleus

Electrons are found in the electron shell.

An electron is negatively charged while a proton is positively charged.


http://www.google.com.sg/imgres?imgurl=http://www.scioly.org/w/images/1/1b/Electron_shell_011_Sodium.svg.png&imgrefurl=http://www.scioly.org/wiki/GMOA_Notes&usg=__BWr41JgSP1sAjIKSHoywbKX933Q=&h=194&w=180&sz=10&hl=en&start=14&zoom=1&itbs=1&tbnid=M0tsb3vKAyYmyM:&tbnh=103&tbnw=96&prev=/images%3Fq%3Dthe%2Batomic%2Bstructure%2Bof%2Ba%2Bsodium%2Batom%2Band%2Ba%2Bsodium%2Bion.%26hl%3Den%26gbv%3D2%26biw%3D1003%26bih%3D622%26tbm%3Disch&ei=w7MZTqOSLsXVrQfGzPzPAQ