Question 5

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) Normal Equation: ZnCO3(s) + 2H⁺Cl⁻ (aq) ---> Zn²⁺Cl⁻2 (aq) + H2O (L) + CO2 (g)
Ionic Equation: ZnCO3(s) + 2H⁺(aq) ---> Zn²⁺(aq)  H2O (L) + CO2 (g)


ii) Excess Zinc Carbonate will ensure that the hydrochloric acid is completely reacted.


iii) After adding Zinc Carbonate to hydrochloric acid until excess zinc carbonate is seen. we then filter these excess zinc carbonate out using a filter funnel and at the same time transfer the solution( ZnCl2) to a beaker. Evaporated the solution to remove water till its a saturated solution. When cooled the zinc chloride crystals will formed and can be obtained.

Question 4.

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) Titration is used for soluble Group(I) or ammonium salts, since potassium is an element from Group(I) and is also soluble titration is used to prepare its salt.


ii) Normal Equation: 2K⁺OH^- (aq) + H⁺2SO4²⁻(aq) ---> K2⁺SO4²⁻(aq) + 2H20 (L)
Ionic Equation: 2OH^- (aq) + H⁺2 ---> 2H20 (L)

Question 3

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


iii)  iron(ii)

Question 2

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) + 2H20 (L) + 2NH3 (g) 


ii) Use damp red litmus paper on gas and it will turn blue if its NH3.

Question 1

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)The Salt is Ammonium Nitrate. The Base is Zinc Hydroxide.


ii)A white precipitate is formed during the reaction.


iii)Zn(NO3)2(aq)  + 2NH4OH(aq) ---> 2NH4(NO3)(aq) + Zn(OH)2 (s)


iv)Normal Equation:Zn²⁺(NO3)-2(aq)  + 2NH4⁺ OH-(aq)--->2NH4

⁺

(NO3) ⁻(aq) + Zn(OH)2 (s)
Ionic Equation:Zn²⁺ (aq) + 2OH^- (aq) ---> Zn(OH)2 (s)

Comments

Xin Kang
Hi Xin Kang!!!=) Guess I'll just post mu comments here too... Well, Overall I think the answers are good and easy to understand butshould't the relative mass of electrons be 1/1840?0.0And i told you in school before but you explanation in Q.3 is Sulfide ion not Sulfur ion=) Please comment on my too!!The last comment is sure to get you 1 mark you know XD
ZW
Helmi
Hi Helmi! Here are my comments for your answers. Firstly, i really like the picture from the website you posted in question 2(really clear and easy to understand)^^. Your answers are detailed and imformative. And of course it jolted my memory on anions which i had forgotton about.
ZW
Fabian
Hi Fabian! Comments on your answers are here!=) For Q.5 your first comparision on why sodium is metal and sulfur a non-metal was very good i didn;t think of that answer before i read yours. For question 1 there are no problems with it but i would't hurt to list down to relative mass too.=)

ZW

Photos Of Me,Family And Friends

2E7 Class Outing- In Which 2E7 were all brutally torn apart as a class to a new one.

Hong Kong- In Which I Showed Albert Einstein Louis Obisai Vallina Extreme(Stitch) And he was totally captivated by his L.O.V.E

Universal Studios- In Which Frankenstein tries to strangle my sister and we were still smiling at the camera.

5. Sodium is a metal and sulfur is a non-metal....why we classify them this way??'
As sodium is a conductor of heat and electricity one of the basic properties for a metal whereas sulfur does not conduct heat or electricity making it the insulator of heat and electricity therefore they are non-metals.

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.
Chlorine-35 have 17 protons and 18 neutrons whereas chlorine-37 have 17 protons too but have 20 neutrons since Chlorine-37 have a different number of neutrons than Chlorine-35 they are isotopes.

3. Draw the atomic structure of a sulfur atom and a sulfide ion....explain why you draw it this way.
The sulfur has a electric configuration of (2.8.6) thus giving it its 3 shells with the last having only 6 electrons. For the sulfide, it has gain two electrons making it stable and thus giving it its full 3 shells.
Sulfur

 Sulfide

2. Draw the atomic structure of a sodium atom and a sodium ion....explain why you draw it this way.( The crosses are a bit faint(sry) look closely and you can see it =) )
Firstly, the a sodium atome will have the electric configuration of (2.8.1) therefore having three shells, the first shell accept 2 electron while the second 8, the third is left with the extra 1 electron. For the Sodium Ion the sodium have an extra one electron had give it away to become stable therefore resulting in the 2 shells.
Sodium Atom

 Sodium Ion

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 is like a spherical object with the nucleus in the middle, electrons are "orbiting" around this nucleus. The sub-atomic particles in the atom are electrons with a relative mass of 1/1840 and a relative charge of -1. Neutrons will be another sub-particle in the atom, it has a relative mass of  1 and a relative charge of 0. Next, we have the protons, protons have a relative mass of 1 and a charge of +1. There is also the nucleus which contains protons and neutrons in it.