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

i) Name the salt and the base.

Ans: The salt is ammonium nitrate and the base is zinc hydroxide.

ii) Describe the observations for the reaction.

Ans: When zinc nitrate reacts with aqueous ammonia, white precipitation is form. The white precipitate is soluble in excess to give a colourless solution.

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

Ans: Zn(NO3)2 (aq) + 2NH4OH (aq) à Zn(OH)2 (s) + 2NH4NO3 (aq)

iv) Write an ionic equation for the reaction.

Ans: : Zn2+ (aq) + 2OH- (aq) àZn(OH)2 (s)

Q2. Ammonium sulfate is heated with sodium hydroxide.

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

Ans: 2(NH4)2SO4 (aq) + 2NAOH (aq) à 2NH3 (g) + 2H2O (l) + Na2SO4 (aq)

ii) Describe a test for the gas.

Ans: The gas formed is ammonia. Hold a piece of dump red litmus paper over the mouth of the test tube. The ammonia gas will turn the damp 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.

Ans: The gas evolved is ammonia gas.

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

Ans: The anion is nitrate (NO3-).

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

Ans: One possible cation will be Iron (II), Fe2+.

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.

Ans: Potassium sulfate is a group (I) and soluble salt. 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.

Ans: 2H+ (aq) + OH- (aq) à H2O

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

i) Write an ionic equation for the reaction.

Ans: CO32+ (aq) +2H+ (aq) à H2O (l) +CO2 (g)

ii) Why excess zinc carbonate is used?

Ans: To ensure that all the hydrochloric acid is completely reacted.

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

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

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

 Step 3: Evaporate the zinc chloride solution to remove the water and to obtain a saturated salt solution.

  Step 4: Leave the hot saturated solution to cool down and to form zinc chloride crystals.

Comments on friends' chemistry blog

1. Aleen (27)
-Her answers are very detailed and informative. Besides pictures from the internet, she also took photos of her drawings. Her drawings are very neat and tidy. She also answered the questions very well. But I think she wrote wrongly for the sodium ion, it should be Na not S and outside the brackets of sodium ion should be + not 1+. She gave a lot of elaboration for each question. I think she did a lot of research.

2. Su(24)
-Her answers are good and detailed. She included some examples to relate to her answers. Her answers (especially for the first question) was quite lengthy so I think she must have done a lot of research.  But I think for question 5, it will be better if she can add in the physical properties. For sulfide ion, there should be a (2-) outside bracket.

3. Agnes(14)
-Her blogskin is very beautiful. Her blog is interesting as she included pictures for almost every single question. There are pictures of her drawings and from the internet. Her answers are very detailed. Her answers are straight-forward and easy to understand. She has made good explanations for her answers and relate the answers to her drawings. I think she has put in a lot of effort for the answers.

Japan Trip Photos! :)

~Piano~

Papa, Mama

Chihiro reading comic book.

My "Thankyou" letter is pinned on her wall! :)

Chi-Chi's room

Clarinet"o"

Say "Kawaii"!

WSL-08-002 篤姫メインテーマ（吹奏楽セレクション）

Atomic Structure Assignment

 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/s. The sub-atomic particles within are its protons, neutrons and electrons. Protons and neutrons can be found in the nucleus while electrons are found in its electron shell. Protons are positive (+1 charge) with a relative mass of 1, neutrons are neutral with a relative mass of 1 while electrons are negative (-1 charge) with a relative mass of roughly 1/1840.

Why chlorine has an average mass of 35.5?

Chlorine-35: 75% abundance in chlorine atoms

Chlorine-37: 25% abundance in chlorine atoms

Average: (75/100 x 35) + (25/100 x 37) = 35.5 (periodic table no. for Chlorine)

Simple & Short question

Which element is heavier?

Answer: Chlorine!

Reason: Look at the nucleon number/mass number/Ar (relative atomic mass)

Which number is bigger?- 35 or 23?

Atomic Structure Assignment (Question 5-answer)

Q5)Sodium is a metal and sulfur is a non-metal....why we classify them this way??'
Physical properties:
Sodium-conduct electricity and heat
Sulfur-does not conduct electricity and heat (insulator)
Sodium has a greater melting and boiling point than Sulfur.

Chemical properties
Sodium-(2.8.1) LOSE 1 electron to complete the valence shell, to make it stable.
Sulfur-(2.8.6) GAIN 2 electrons to complete the valence shell, to make it stable.

Atomic Structure Assignment (Question 4-answer)

Q4)Chlorine-35 atom and Chlorine-37 atom are called isotopes...Use these two examples to explain what is 'isotopes'.

Chlorine-35    
Nucleon number: 35
Proton number: 17
Neutron number: 18 (35-17=18)
Electron number: 17 (same as proton no.)



Look at chlorine-37, RIGHT SIDE

 Chlorine-37
Nucleon number:37
Proton number: 17
Neutron number: 20 (37-17=20)
Electron number: 17 (same as proton no.)

DEFINITION-Isotopes: Different atoms of the same element which have the same number of protons but different number of neutrons.

Chlorine-35 has 18 neutrons whereas Chlorine-37 has 20 neutrons. (Different)
Chlorine-35 and Chlorine-37 both have 17 protons. (Same)
Of course, both are of the same element.-> chlorine (Same)
Since, their nucleon number is different, therefore, they are ISOTOPES! :)

Atomic Structure Assignment (Question 3-answer)

Q3)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 of (2.8.6) so it has 6 electrons on its valence shell.

-The sulfur ion is drawn this way as it gains 2 electrons on the valence shell and become stable, which means that its electronic configuration is (2.8.8).