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