2P07: When Alkali Meets Ammonium Salts... (Answer Scheme)

Sodium hydroxide + ammonium chloride

: Colour of gas - colourless
: Odour of gas - pungent
: Effect of gas on red litmus paper - Damp red litmus paper turns blue
: Effect of gas on blue litmus paper - No visible changes
: Name of gas formed - ammonia

Calcium hydroxide + ammonium nitrate

: Colour of gas - colourless

: Odour of gas - pungent

: Effect of gas on red litmus paper - Damp red litmus paper turns blue

: Effect of gas on blue litmus paper - No visible changes

: Name of gas formed - ammonia

1. Ammonium gas

2. Ammonium salts + alkali --> salt + water + ammonium gas

3. This way, the gas will evaporate from the solution, and we are able to carry out the experiment.

4. Ammonia gas is alkaline.

5. An alkali will only show its alkaline properties in the presence of water. 

6. Add sodium hydroxide to substance X and heat it. Ammonia gas would escape. It would be a colourless and pungent gas. If the red litmus paper turns blue, X is an ammonium salt.

7. Ammonium nitrate can react with calcium hydroxide to form calcium nitrate, water and ammonia. The ammonia will increase the pH for the soil, thus making it not suitable for the plants. 

Exercise

1(a) Sodium chloride + water + ammonia

1(b) NaOH + NH4Cl --> NaCl + H2O + NH3

2(a) Sodium sulfate + water + ammonia

2(b) 2NaOH + (NH4)2SO4 --> Na2SO4 + 2H2O + 2NH3 

3(a) Sodium nitrate + water + ammonia

3(b) NaOH + NH4NO3 --> NaNO3 + H2O + NH3

4(a) Calcium chloride + water + ammonia
4(b) Ca(OH)2 + 2NH4Cl --> CaCl2 + 2H2O + 2NH3

5(a) Calcium sulfate + water + ammonia
5(b) Ca(OH)2 + (NH4)2SO4 --> CaSO4 + 2H2O + 2NH3

6(a) Calcium nitrate + water + ammonia
6(b) Ca(OH)2 + 2NH4NO3 --> Ca(NO3)2 + 2H2O + 2NH3

2p06 answer scheme

Observation: A white solid is formed.  It tastes salty.

Conclusion: An acid reacts with an alkali to produce salt and water. 

Exercise

Q1. (a) hydrochloric acid + sodium hydroxide à sodium chloride + water

       (b) HCl + NaOH à NaCl + H2O

Q2. (a) Hydrochloric acid + potassium hydroxide à Potassium chloride + water

       (b) HCl + KOH à KCl + H20

Q3. (a) Hydrochloric acid + calcium hydroxide à Calcium chloride + water

       (b) HCl + CaOH à CaCl + H2O

Q4. (a) nitric acid + sodium hydroxide à sodium nitrate + water

       (b) HNO3 + NaOH à NaNO3 + H2O

Q5. (a) nitric acid + potassium hydroxide à potassium nitrate + water

       (b) HNO3 + KOH à KNO3 + H2O

Q6. (a) sulfuric acid + calcium hydroxide à Calcium sulfate + water

       (b) H2SO4 + CaOH à CaSO4 + H2O

Q7. (a) sulfuric acid + sodium hydroxide à sodium sulfate + water

       (b) H2SO4 + NaOH à NaSO4 + H2O

Q8. (a)sulfuric acid + potassium hydroxide à potassium sulfate + water

       (b) H2SO4 + KOH à KSO4 + H2O

2P05 - When dilute acids meet carbonates

1. Dilute acid reacts with a carbonate to produce carbon dioxide gas.


2. Metal carbonate  + Acid --> Salt + Water + Carbon Dioxide


3.  Differences:
(a) Effervescence of colourless and odourless gas which formed a white precipitate in limewater was observed in the first experiment; while no gas was evolved in this experiement.


(b) A white precipitate is formed in limewater in the first experiment while there is no visible change in this experiment.


(c) The damp blue litmus paper turned red in the first experiment, while there is no visible change in this experiment.


Explanation:


The reaction between calcium carbonate and sulfuric acid is imcomplete. The product, calcium sulfate is insoluble in water. It will form a coating around the insoluble calcium carbonate. Hence prevent further reaction from taking place.


4. Bubble the gas through limewater (you do not put the gas in limewater). If the gas is carbon dioxide, a white precipitate is formed. (You do not use the word "chalky")


5. a) Carbon dioxide is acidic.
    b) Bubble the sample of air through limewater. carbon dioxide gas in the air will react with limewater to form an insoluble product, calcium carbonate. Thus removing carbon dioxide from the air.


EXERCISE:


1a. Hydrochloric acid + calcium carbonate ---> calcium chloride + carbon dioxide + water
  b. CaCO₃ + 2HCl ---> CaCl₂ + CO₂ + H₂O


2a. Hydrochloric acid + sodium carbonate ---> sodium chloride + carbon dioxide + water
  b. Na₂CO₃ + 2HCl ---> 2NaCl + H₂O + CO<sub>2


3a.</sub> Potassium carbonate + Hydrochloric acid ---> potassium chloride + carbon dioxide + water
  _b. K2CO3 + 2HCl --> 2KCl + H2O + CO2


_{4a.  Calcium} carbonate + Nitric acid  _{--->Potassium nitrate + carbon dioxide + water
  b.}  2HNO3 + CaCO3 = Ca(NO3)2 + H2O + CO2


5a. Sodium carbonate + nitric acid ---> Sodium nitrate + carbon dioxide + water
  b. NaC03 + HNO3 ----> NaNO3 +H20 + CO2

6a. Potassium carbonate + Nitric acid ---> potassium nitrate + carbon dioxide + water

 b. K2CO3 + 2HNO3 ---> 2KNO3 + CO2 + H2O

7a. Calcium carbonate + Sulfuric acid ---> Calcium sulfate + carbon dioxide + water

 b. CaCO3 + H2CO4 = CaSO4 + CO2 + H2O 

8a.  Sodium carbonate + Sulfuric acid ---> Sodium sulfate + carbon dioxide + water 

 b.  Na2CO3 + H2SO4 => Na2SO4 + CO2 + H2O

9a. Potassium carbonate + Sulfuric acid ---> Potassium sulfate + carbon dioxide + water 

  b. K2CO3 + H2SO4 → K2SO4 + CO2 + H2O

10a. Sodium carbonate + Ethanoic acid ---> Sodium ethanoate + carbon dioxide + water 

  b.  Na₂CO_{3 +} 2CH3COOH ---> 2NaC2H3O2 + CO2 +H2O

11a. Potassium carbonate + Ethanoic acid ---> Potassium ethanoate + carbon dioxide + water

   b. K₂CO_{3 +} 2CH3COOH ---> 2CH₃CO₂K + CO2 + H2O

12a. Calcium carbonate + Ethanoic acid ---> Calcium ethanoate + carbon dioxide + water 

   b. CaCO_{3 +} 2CH3COOH ---> Ca(C₂H₃O₂)₂ + CO2 + H2O


Done by:

Bryan Chia Jun Qing (5)

Koh Kai Jie (14)

Soh Han Qiang (23)

Yap Jun Lin (32)

2P04 Answers(Done by Chairul Karim,Johny Zou Rui,Ng Sze Hian and Jesse Tan)

1. salt + hydrogen gas
2. Acid + Metal --> salt + hydrogen gas
3. Use a burning splint and if a 'pop' sound is heard, there is hydrogen gas present.
4. It is a neutral gas.
5. Magnesium, zinc,iron, copper

Exercise


1(a) magnesium + hydrochloric acid --> magnesium chloride + hydrogen gas
  (b) Mg + 2HCl --> MgCl2 + H2

2(a) iron + hydrochloric acid --> iron(II) chloride + hydrogen gas
  (b) Fe + 2HCl --> FeCl2 + H2

3(a) zinc + hydrochloric acid --> zinc chloride + hydrogen gas
  (b) Zn + 2HCl --> ZnCl2 + H2

4(a) magnesium + sulfuric acid --> magnesium sulfate + hydrogen gas
  (b) Mg + H2SO4 --> MgSO4 + H2

5(a) iron + sulfuric acid --> iron(II) sulfate + hydrogen gas
  (b) Fe + H2SO4 --> FeSO4 + H2

6(a) zinc + sulfuric acid --> zinc sulfate + hydrogen gas
  (b) Zn + H2SO4 --> ZnSO4 + H2

7(a) magnesium + nitric acid --> magnesium nitrate + hydrogen gas
  (b) Mg + 2HNO3 --> Mg(NO3)2 + H2

8(a) iron + nitric acid --> iron(II) nitrate + hydrogen gas
  (b) Fe + 2HNO3 --> Fe(NO3)2 + H2

9(a) zinc + nitric acid --> zinc nitrate + hydrogen gas
  (b) Zn + 2HNO3 --> Zn(NO3)2 + H2

2P06 Answers (By Group 6)

Practical 2P06 Answers

Observations: A white precipitate is formed and it tastes salty

Conclusion: Acid reacts with alkali to produce salt and water

Exercise

1a) Hydrochloric acid + Sodium Hydroxide à Sodium Chloride + Water

1b) HCl + NaOH à NaCl + H2O

2a) Hydrochloric acid + Potassium Hydroxide à Potassium Chloride + Water

2b) HCl + KOH à KCl + H2O

3a) Hydrochloric acid + Calcium Hydroxide à Calcium Chloride + Water

3b) 2HCl + Ca(OH)2 à CaCl2 + 2H2O

4a) Nitric Acid + Sodium Hydroxide à Sodium Nitrate + Water

4b) HNO3 + NaOH à NaNO3 + H2O

5a) Nitric acid + Potassium Hydroxide à Potassium Nitrate + Water

5b) HNO3 + KOH à KNO3 + H2O

6a) Nitric acid + Calcium Hydroxide à Calcium Nitrate + Water

6b) 2HNO3 + Ca(OH)2 à Ca(NO3)2 + 2H2O

7a) Sulfuric acid + Sodium Hydroxide à Sodium Sulfate + Water

7b) H2SO4 + 2NaOH à Na2SO4 + 2H2O

8a) Sulfuric acid + Potassium Hydroxide à Potassium Sulfate + Water

8b) H2SO4 + 2KOH à K2SO4 + 2H2O

9a) Sulfuric acid + Calcium Hydroxide à Calcium Sulfate + Water

9b) H2SO4 + Ca(OH)2 à CaSO4 + 2H2O

10a) Hydrochloric acid + Ammonia solution à Ammonium Chloride + water

10b) NH3 + H2O --> NH4OH

11a) Nitric acid + Ammonia solution à Ammonium gas + Nitrate

10b) NH3 + H2O --> NH4OH

12a) Sulfuric acid + Ammonia solution à Ammonium Sulfate + water

12b) H2SO4 + 2NH4OH à (NH4)2SO4 + 2H2O

Group 3--2P04 Answer Scheme

1. What can you conclude ablut the reaction between some dilute acids and some metals?

Ans:    Dilute acids react with reactive metals to produce salt and hydrogen gas.

2. Write the general equation for the reaction between dilute acid and metal.

Ans:    Dilute Acid + Metal --> Salt + Hydrogen Gas

3. How can you identify the gas formed when some dilute acids react with some metals?

Ans:    We can place a lighted splint inside the test tube and if hydrogen is present, a 'pop' will be heard.

4. From the effect of gas damp litmus paper, what can you conclude about the nature of hydrogen gas?

Ans:    Hydrogen gas is neutral.

5. Arrange the metals according to their reactivity in descending order. (most reactive first)

Ans:    Iron(Fe), Magnesium(Mg), Zinc(Zn), Copper(Cu)

Exercise

1(a) magnesium + hydrochloric acid --> magnesium chloride + hydrogen gas
  (b) Mg + 2HCl --> MgCl2 + H2

2(a) iron + hydrochloric acid --> iron(II) chloride + hydrogen gas
  (b) Fe + 2HCl --> FeCl2 + H2

3(a) zinc + hydrochloric acid --> zinc chloride + hydrogen gas
  (b) Zn + 2HCl --> ZnCl2 + H2

4(a) magnesium + sulfuric acid --> magnesium sulfate + hydrogen gas
  (b) Mg + H2SO4 --> MgSO4 + H2

5(a) iron + sulfuric acid --> iron(II) sulfate + hydrogen gas
  (b) Fe + H2SO4 --> FeSO4 + H2

6(a) zinc + sulfuric acid --> zinc sulfate + hydrogen gas
  (b) Zn + H2SO4 --> ZnSO4 + H2

7(a) magnesium + nitric acid --> magnesium nitrate + hydrogen gas
  (b) 2Mg + 2HNO3 --> 2MgNO3 + H2

8(a) iron + nitric acid --> iron(II) nitrate + hydrogen gas
  (b) 2Fe + 2HNO3 --> 2FeNO3 + H2

9(a) zinc + nitric acid --> zinc nitrate + hydrogen gas
  (b) 2Zn + 2HNO3 --> 2ZnNO3 + H2

Done by: Cheh Fu Yang
              Wesley Kam
              Nesman Ng
               joker Tan Zi Jie

2P05: When Dilute Acid Meet Carbonates...

1. They react to form sodium chloride solution and carbon dioxide. Extra water is also formed but that is already present in the HCl solution.

2. Metal Carbonate + Acid -> Salt + Water + Carbon Dioxide

3a) It will be more reactive.
 b) There will be more carbon dioxide.
 c) The limewater will turn chalky faster.
 Explanation: Sulfuric is a weaker acid, thus it reacts faster.

4. The gas can be put into limewater and if it turns chalky, it is carbon dioxide.

5a. Acidic.
 b. Some dilute acid and extract the one which is chemically neutral.

Exercise
1a)1.      Calcium carbonate + hydrochloric acid ---> calcium chloride + carbon dioxide + water

CaCO₃ + 2HCl ---> CaCl₂ + CO₂ + H₂O

2.       Sodium carbonate + Hydrochloric acid -->sodium chloride + carbon dioxide + water
Na₂CO_3(aq) + 2HCl(aq) --> 2NaCl(aq) + CO_2(g) +H₂O(l)


3.       Potassium carbonate + hydrochloric acid -->potassium chloride, water and carbon dioxide

K2CO3 + 2HCl --> 2KCl + H2O + CO2

4.       Calcium carbonate + nitric acid -->water + carbon dioxide + calcium nitrate
CaCO₃ + 2HNO₃ ^-------> H₂O + CO_{2 +} CA(NO₃⁾₂

        5.  Sodium carbonate + nitric acid --> water + carbon dioxide + sodium nitrate          Na₂CO₃  + 2HNO_{3 -->} H₂O + CO_{2 +} Na(NO₃)

         6. potassium carbonate + nitric acid -->water + carbon dioxide + potassium nitrate   K₂CO₃ + 2HNO_3  -->H2O + CO2 + KNO₃

7a) 2NaOH + H2SO4 -> (Na)2SO4 + 2H20
  b) Sodium hydroxide + sulfuric acid -> sodium sulfiate + water

8a) 2KOH + H2SO4 --> K2SO4 + 2H2O
  b) Sulfuric acid + potassium hydroxide -> potassium sulfate + water

9a) H2SO4 + Ca(OH)2 --> CaSO4 + 2H2O
  b) sulfuric acid + calcium hydroxide --> calcium sulfate + water

10) HCL + NH3 --> NH4CL
  b) hydrochloric acid + ammonia solution --> ammonium chloride

11a) HNo3 + NH3 -> H2O + NH4NO3
   b) nitric acid + ammonia solution -> water + ammonium nitrate

Done by: Keif Tan
              Wan Wei Ren
              Tan Nigel

2P03 answers

Part 1 (in order)
1,1,1,1,2,3,5,8,9,10,14

Part 2 (pH)
Initial: 1
Final:7

Excercise
1(i) hydrochloric acid and sodium hydroxide
answer: hydrochloric acid + sodium hydroxide --> sodium chloride + water

(ii) hydrochloric acid and copper(II) oxide
answer: hydrochloric acid + copper(II) oxide --> copper(II) chloride + water

2) 13, 13, end, point, neutralistaion

3) increases, decreases

4(i) pH = 14
(ii) pH = 7

Done by Group 1
Terence Han,
Joseph Tan
Ng Kee Hsien
Wesley Chai

Yeo Feng Rui

The compound that i have chosen is Acetic Acid. Its symbol is CH3COOH. It is an organic acid that gives vinegar its sour taste and pungent smell. It is a weak acid, in that it is only a partially dissociated acid in an aqueous solution. Pure, water-free acetic acid (glacial acetic acid) is a colourless liquid that absorbs water from the environment (hygroscopy), and freezes at 16.5 °C (62 °F) to a colourless crystalline solid. The pure acid and its concentrated solutions are very corrosive.

Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5730 years.

Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u, hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's chemical elemental mass. It is highly flammable and ignites instantly when in contact with heat. It is colourless, odourless, nonmetallic and tasteless at room temperature.

Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς (oxys) (acid, literally "sharp", referring to the sour taste of acids) and -γενής (-genēs) (producer, literally begetter), because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless, odorless, tasteless diatomic gas with the formula O_2.

Eric Seow (8)

Sulfur Trioxide is the chemical compound with the formula SO_{3.   It is the primary agent of acid rain.}

_Formation

_{Sulfur Trioxide- 3 Oxygen atoms + 1 Sulfur atom}

In terms of electron-counting formalisms, the three oxygen atoms are in the -2 oxidation state and the sulfur atom has an oxidation state of +6, a formal charge of 0, and is surrounded by 6 electron pairs. 

_{Constituent Elements}

 The most important use of oxygen is for breathing. Animals require oxygen in their air (or water) to live.

Another use for oxygen is for oxidation reactions -- the most obvious
example is burning.  Fires require oxygen to burn. 

Bonding 

Sulfur trioxide is formed from a covalent bond.  

Dot and cross diagram

 

Sun Yu Hsiang (25)

The harmful compound that I chose is Cobalt Oxide.  It is made up of 1 cobalt atom (Co) and 1 oxygen atom (O).  Its atomic symbol is CoO.  These 2 elements bond using ionic bonding.  Cobalt is a harmless metal, while oxygen is a harmless gas.  However, Cobalt Oxide is dangerous to humans and harmful to the environment.

Dot-and-Cross Diagram:

Declan Lee

Lithium oxide (Li₂O) or lithia is aninorganic chemical compound. Lithium oxide is formed along with small amounts of lithium peroxide when lithium metal is burned in the air and combines with oxygen.

Nitrogen dioxide

Nitrogen dioxide is the chemical compound with the formula NO₂. One of several nitrogen oxides, NO₂ is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent air pollutant. Nitrogen dioxide is a paramagnetic bent molecule with C_2v point group symmetry.

covalent bond

Joseph Tan :)

Hydrogen Bromide is the diatomic molecule HBr. HBr is a gas at standard conditions. Hydrobromic acid forms upon dissolving HBr in water. Conversely, HBr can be liberated from hydrobromic acid solutions with the addition of a dehydration agent, but not by distillation.
At room temperature, HBr is a nonflammable gas with an acrid odor, fuming in moist air because of the formation of hydrobromic acid. HBr is very soluble in water, forming hydrobromic acid solution, which is saturated at 68.85%. Aqueous solutions that are 47.38% HBr by weight form a constant-boiling mixture that boils at 126°C.
There are many uses of HBr in chemical synthesis. For example, HBr is used for the production of alkyl bromides from alcohols.
Hydrogen is an element with an atomic number of 1. It is the lightest and most abundant chemical element. Bromine has an atomic number of 35 and an atomic mass of 79.904.

Chairul Karim (2)

Hydrogen Peroxide(H2O2)

Covalent Bonding

It is made up of 2 hydrogen atoms and 2 oxygen atoms. The 2 hydrogen atoms share one electron and then the 2 hydrogen atoms share an electron each to each side of the oxygen atoms, thus forming the compound.

Nigel Tan's Post (22)

Octyl methodxycinnamate. Used in sunscreen and eventually sinks into the deeper layers of the skin and makes the top layer vulnerable.

Koh Kai Jie

Carbonic Acid


Carbonic Acid is made up of Hydrogen(H), Carbon(C) and Oxygen(O2)

Carbonic Acid is formed naturally in our blood and is the indicator the body uses when it lacks air. this will cause fainting and drowning.

Kee Hsien's post- Sodium Bromide

Sodium bromide- made of Sodium(Na) and bromine(Br)

Sodium bromide (NaBr).
Composed of Sodium (Na) which is from the 3rd element of Group 1. It is the largest atom of its period, however still relatively small.

1st Ionization Energy: 495.8 kJ·mol−1
Electronegativity: 0.93 (Pauling scale)

and Bromine (Br) with is the 3rd element of Group 17. It is a small atom, given its position on the right side of the periodic table.

1st Ionization Energy:  1139.9  kJ·mol−1
Electronegativity: 2.96 (Pauling scale)

Sodium bromide (NaBr) is a single salt clear brine fluid that has the following features and benefits:

• It is non-damaging to the formation,
• It is thermally and chemically stable,
• It can be blended with other solutions of bromides and chlorides, and
• It is especially useful when used in formations that are known to have calcium sensitivity.

A 44.7 percent aqueous solution of sodium bromide has a density of 12.4 pounds per gallon and a crystallization temperature (LCTD) of 41°F (5°C).
A pure sodium bromide (NaBr) brine fluid is often selected when the chloride ion is not desirable and when sodium is preferred over calcium. It is often used in situations where formation waters contain high levels of sulfate or carbonate that may precipitate with the calcium ion.