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Questions and Answers
Why is an inverted funnel used when dissolving ammonia gas in water?
Why is an inverted funnel used when dissolving ammonia gas in water?
- To increase the rate of diffusion of ammonia gas.
- To ensure that the ammonia gas is evenly distributed in the water.
- To prevent the ammonia gas from reacting with the air.
- To prevent sucking back by increasing the surface area for dissolving. (correct)
Which of the following statements accurately describes the reaction between rust (hydrated iron(III) oxide) and vinegar (ethanoic acid)?
Which of the following statements accurately describes the reaction between rust (hydrated iron(III) oxide) and vinegar (ethanoic acid)?
- Ethanoic acid acts as a catalyst, speeding up the oxidation of iron(III) oxide.
- Ethanoic acid reduces the iron(III) oxide to metallic iron, removing the rust.
- Ethanoic acid, being an acid, reacts with the basic iron(III) oxide to form iron(II) ions and water. (correct)
- Ethanoic acid, being a base, neutralizes the acidic iron(III) oxide, forming a salt and water.
When using calcium oxide to dry ammonia gas, why is it crucial to avoid using anhydrous calcium chloride or concentrated sulfuric acid?
When using calcium oxide to dry ammonia gas, why is it crucial to avoid using anhydrous calcium chloride or concentrated sulfuric acid?
- Anhydrous calcium chloride and concentrated sulfuric acid will only dry the ammonia gas at very high temperatures.
- Anhydrous calcium chloride and concentrated sulfuric acid react violently with calcium oxide, producing toxic gases.
- Anhydrous calcium chloride and concentrated sulfuric acid will cause the ammonia gas to polymerize.
- Ammonia reacts with anhydrous calcium chloride and concentrated sulfuric acid. (correct)
A student tests a solution and finds that it turns methyl orange yellow and phenolphthalein pink. What can be concluded about the pH of the solution?
A student tests a solution and finds that it turns methyl orange yellow and phenolphthalein pink. What can be concluded about the pH of the solution?
Which statement accurately describes why universal indicator is used rather than a pH meter?
Which statement accurately describes why universal indicator is used rather than a pH meter?
How does the presence of carbon dioxide affect the comfort level in the stomach when certain antacids like calcium carbonate ($CaCO_3$) are ingested?
How does the presence of carbon dioxide affect the comfort level in the stomach when certain antacids like calcium carbonate ($CaCO_3$) are ingested?
In the context of removing acidic air pollutants using a scrubber, which of the following options best describes the chemical process involving calcium oxide ($CaO$) and sulfur dioxide ($SO_2$)?
In the context of removing acidic air pollutants using a scrubber, which of the following options best describes the chemical process involving calcium oxide ($CaO$) and sulfur dioxide ($SO_2$)?
When 'fruit salt' is dissolved in water, it produces effervescence. What is the ionic equation for this reaction?
When 'fruit salt' is dissolved in water, it produces effervescence. What is the ionic equation for this reaction?
Why should fizzy drink tablets be stored in a dry place?
Why should fizzy drink tablets be stored in a dry place?
Which of the following is the correct net ionic equation for the reaction between calcium carbonate ($CaCO_3$) and hydrochloric acid ($HCl$)?
Which of the following is the correct net ionic equation for the reaction between calcium carbonate ($CaCO_3$) and hydrochloric acid ($HCl$)?
Flashcards
What is an antacid?
What is an antacid?
A substance that neutralizes excess stomach acid, examples include milk of magnesia.
What is slaked lime?
What is slaked lime?
Used to adjust too acidic soil pH.
What is Calcium sulfite?
What is Calcium sulfite?
Used in scrubbers to remove acidic air pollutants.
Composition of acids
Composition of acids
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What is an alkali?
What is an alkali?
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What is an inverted funnel?
What is an inverted funnel?
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Acid, Base and Neutral solutions
Acid, Base and Neutral solutions
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What is an acid-alkali indicator?
What is an acid-alkali indicator?
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Carbonate reaction with acid
Carbonate reaction with acid
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Effervescence
Effervescence
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Study Notes
- Topic 4 – Acids and Bases: Applications of Neutralization
Antacids
- Antacids like Milk of Magnesia neutralize excess stomach acid.
- Active ingredients include Magnesium Hydroxide (Mg(OH)2) and Aluminum Hydroxide (Al(OH)3).
- Mg(OH)2(s) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)
- Al(OH)3(s) + 3HCl(aq) → AlCl3(aq) + 3H2O(l)
- Some antacids contain Calcium Carbonate (CaCO3), but it can produce carbon dioxide, causing discomfort.
- CaCO3(s) + 2H+(aq) → Ca²+(aq) + CO2(g) + H2O(l)
Slaked Lime/Quicklime
- Used to adjust overly acidic soil pH.
- Active ingredients are Calcium Hydroxide (Ca(OH)2) and Calcium Oxide (CaO).
Scrubbers
- Used to remove acidic air pollutants, such as Sulfur Dioxide (SO2).
- CaO(s) + SO2(g) → CaSO3(s) (Calcium Sulfite).
- Ca(OH)2(aq) + SO2(g) → CaSO3(s) + H2O(l).
Fertilizers
- Ammonia combined with Nitric or Sulfuric acid produces fertilizers.
- HNO3(aq) + NH3(aq) → NH4NO3(aq)
- 2NH3 + H2SO4 → (NH4)2SO4
Rust Remover
- Household chemicals like vinegar can remove rust.
- Vinegar (Ethanoic Acid) reacts with hydrated Iron(III) Oxide (Rust).
- Fe2O3(s) + 6H+(aq) → 2Fe2+(aq) + 3H2O(l)
Acidic Compounds
- Acids must contain hydrogen atoms.
- Sulfure Dioxide (SO2), Nitrogen Dioxide (NO2), Carbon Dioxide (CO2) are acidic.
- Examples: H2SO3, HNO2, HNO3, H2CO3.
Bases/Alkalis
- An alkali is a water-soluble base that reacts with acid to produce salt and water.
- Potassium Hydroxide (KOH) to make drainage cleaner and oven cleaner.
- Sodium Hydroxide (NaOH) to make drainage cleaner and oven cleaner.
- Calcium Hydroxide (Ca(OH)2) to make slaked lime for neutralizing too acidic soil.
- Ammonia (NH3) to make glass cleaner.
- Magnesium Hydroxide (Mg(OH)2) to make antacids.
- Copper (II) oxide (CuO(s)).
Ammonia Ionization
- Ammonia is very soluble in water.
- An inverted funnel is used to prevent sucking back during dissolution.
- NH3(g) + H2O(l) ⇌ NH4+(aq) + OH-(aq)
Preparation of Ammonia
- Warm an ammonium salt with a sodium hydroxide solution.
- Or warm an ammonium salt with a metal oxide.
- Boiling tube is slanted downward to prevent condensed water from flowing back and cracking the hot boiling tube.
- NH3(g) is collected using upward delivery because it's less dense than air.
- Calcium oxide is used as a drying agent for NH3(g).
- Anhydrous calcium chloride and concentrated sulphuric acid cannot be used to dry ammonia as they react with ammonia.
- Test for NH3 gas: NH3(g) will turn moist red litmus paper to blue.
- Test for NH4+ ions: Warm the NH4+ ions with sodium hydroxide solution creating pungent gas that will turn moist red litmus paper to blue.
Properties of Metal Ions
- Metal ions react with NaOH(aq) / NH3(aq) to form precipitates.
- Re-dissolving precipitates:
- Pb(OH)2(s), Zn(OH)2(s), and Al(OH)3(s) re-dissolve in excess NaOH(aq).
- Ag2O(s), Zn(OH)2(s), and Cu(OH)2(s) re-dissolve in excess NH3(aq).
- Neutralization reaction:
- NH3(g) + HCl(g) → NH4Cl(s).
- 2NH3(aq) + H2SO4 → (NH4)2SO4(aq).
The pH Scale
- pH value ranges from 0 to 14 at 25°C.
- All aqueous solutions contain H+(aq) and OH-(aq).
- Acidic: [H+(aq)] > [OH-(aq)]
- Neutral: [H+(aq)] = [OH-(aq)]
- Alkaline: [H+(aq)] < [OH-(aq)]
- Acid-alkali indicator: A dye whose color is sensitive to the [H+(aq)].
- pH Measurement: Universal indicator/pH paper, pH meter.
Skill 1
- Given [H+], find pH
- pH = -log[H+]
Skill 2
- Given pH, find [H+]
- [H+] = 10^(-pH)
Room Temperature
- pH + pOH = 14
- Salts from neutralization may be acidic, neutral, or basic in nature.
Indicators
- Methyl orange, Litmus solution, Phenolphthalein.
Chemical Reactions of Acids
- Reaction with carbonates (CO32-) or hydrogencarbonates (HCO3-).
- Carbonate + Acid → Salt + Carbon Dioxide gas + Water
- Hydrogencarbonate + Acid → Salt + Carbon Dioxide gas + Water
- Effervescence occurs, and carbon dioxide turns limewater milky.
- *Fizzy drink tablets: Contain solid acid and sodium hydrogencarbonate.
- H+(aq) + HCO3-(aq) → CO2(g) + H2O(l)
- *Baking powder: Mixture of sodium hydrogencarbonate and a solid acid. Decomposition releases carbon dioxide to make cakes rise.
- 2NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g).
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