Essential Chemistry Reactions and English Tense Rules

Posted on Oct 8, 2025 in Chemistry

Chemistry Fundamentals

Acids and Bases Classification

Acids (Based on Basicity)

  • Monobasic: HCl, CH3COOH (Acetic Acid)
  • Dibasic: H2SO4 (Sulfuric Acid)
  • Tribasic: H3PO4 (Phosphoric Acid)

Acids (Based on Strength)

  • Strong Acids: HCl, H2SO4, HNO3
  • Weak Acids: CH3COOH, H2CO3 (Carbonic Acid), HCOOH (Formic Acid)

Bases (Based on Acidity)

  • Monoacidic: NaOH, KOH, NH4OH (Ammonium Hydroxide)
  • Diacidic: Mg(OH)2, Ca(OH)2, Fe(OH)2
  • Triacidic: Fe(OH)3

Bases (Based on Strength)

  • Strong Bases: KOH, Ba(OH)2 (Barium Hydroxide)
  • Weak Bases: Ca(OH)2, Mg(OH)2, NH4OH

General Chemical Reactions

  1. Active Metal + Dilute Acid: Salt + H2
  2. Metal Carbonate/Bicarbonate + Dilute Acid: Salt + Water + CO2
  3. Acid + Base (Neutralization): Salt + Water + Heat
  4. Acid + Metal Oxide: Salt + Water
  5. Base + Amphoteric Metal: Metal Salt + H2
  6. Base + Non-Metallic Oxide: Salt + H2O

Chemical Indicators and Color Changes

IndicatorNeutralAcidicBasic
LitmusPurpleRedBlue
Red Cabbage ExtractRedRedGreen
PhenolphthaleinColorlessColorlessPink
Methyl OrangeOrangeRedYellow

Key Chemical Equations

Combination and Exothermic Reactions

  • CaO + H2O → Ca(OH)2 + Heat (Exothermic)
  • C + O2 → CO2
  • 2H2 + O2 → 2H2O
  • C + O2 → CO2 + Heat

Decomposition Reactions

  • 2H2O (l) → 2H2 (g) + O2 (g) (Requires Electric Current)
  • CaCO3 → CaO + CO2
  • 2Pb(NO3)2 → 2PbO + 4NO2 + O2 (Brown NO2 gas)
  • 2FeSO4 → Fe2O3 + SO2 + SO3
  • 2AgCl → 2Ag + Cl2
  • 2AgBr → 2Ag + Br2

Displacement Reactions

  • Zn + CuSO4 → ZnSO4 + Cu
  • Fe + CuSO4 → FeSO4 + Cu
  • Zn + 2HCl → ZnCl2 + H2
  • Mg + 2HCl → MgCl2 + H2

Double Displacement Reactions

  • Na2SO4 + BaCl2 → BaSO4↓ + 2NaCl (White precipitate)
  • Pb(NO3)2 + 2KI → PbI2↓ + 2KNO3 (Yellow precipitate)

Other Important Reactions

  • Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 (Requires Sunlight)
  • Copper Corrosion: 2Cu + H2O + CO2 + O2 → Cu(OH)2·CuCO3 (Basic copper carbonate)
  • Silver Tarnish: 2Ag + H2S → Ag2S + H2
  • Iron Rusting: 4Fe + 3O2 + 6H2O → 4Fe(OH)3 → Fe2O3·xH2O

Summary of Acid and Base Properties

  • Acids: React with metals to produce H2 gas; React with bases to form salt + water (neutralization); Conduct electricity in aqueous solution (electrolytes). Examples: Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Acetic acid (CH3COOH).
  • Bases: React with acids to form salt + water; Conduct electricity in aqueous solution. Examples: Sodium hydroxide (NaOH) – Caustic Soda, Calcium hydroxide (Ca(OH)2) – Lime Water, Ammonium hydroxide (NH4OH).

English Grammar Essentials

Verb Tenses and Usage

Simple Present

Used for habits, general truths, exclamations, scheduled future events, and narratives.

Simple Past

Used for actions completed in the past, past habits, and simultaneous actions in the past.

Simple Future

Used for actions one thinks or believes will happen in the future.

Present Continuous (Be + V-ing)

Used for actions currently going on, annoying habits, actions planned in the near future, and temporary actions.

Past Continuous (Was/Were + V-ing)

Used for actions continuing in the past, often used with always or continually.

Future Continuous (Will Be + V-ing)

Used for actions which will be going on at a specific time in the future, or actions planned for the future.

Present Perfect (Has/Have + V3)

Used for actions just completed, describing past events, past experiences without specific time, or past actions continuing in the present.

Past Perfect (Had + V3)

Used for actions completed before a moment in the past, actions taken place before another had begun, unfulfilled desires, or relating two actions in the past.

Future Perfect (Will Have + V3)

Used for actions that will be completed by a specific time in the future.

Present Perfect Continuous

Used for actions that began at some time in the past and are still continuing.

Past Perfect Continuous

Used for actions that began in the past and continued up to a specific time in the past.

Future Perfect Continuous

Used for actions in progress over a period of time that will end in the future.

Conditional Sentence Types

Structure: If Clause, Main Clause

  1. Type 0 (General Truth)
    • Structure: If + Simple Present, Simple Present
  2. Type 1 (Likely Future)
    • Structure: If + Simple Present, Will + V1
  3. Type 2 (Unlikely/Hypothetical)
    • Structure: If + Simple Past, Would + V1
  4. Type 3 (Impossible Past)
    • Structure: If + Past Perfect, Would/Could/Etc. + Have + V3