Qualitative Inorganic Salt Analysis Procedures
Preliminary Tests
| Experiment | Observation | Inference |
| Color of the salt | Colourless | Absence of Cu2+, Fe2+, etc. |
| Odour of the salt | Ammoniacal smell Vinegar smell | NH4+ Acetate ion |
| Solubility | In water with no precipitate with Na2CO3 In dilute HCl, soluble | NH4+ No Group 1 cations |
| Salt is heated in a dry test tube | Colorless gas turns lime water milky Reddish brown fumes Smell of ammonia Pleasant fruity smell | Carbonate Nitrate ion NH4+ Acetate ion |
| Flame test | Pale green Brick red | Ba2+ Ca2+ |
| Ash test | Blue ash | Al3+ |
Systematic Analysis for Anions
| Experiment | Observation | Inference |
| Dilute |
Inorganic Chemistry Notes: Hydrides, Oxides & Metallurgy
Inorganic Chemistry Notes: Hydrides, Oxides & Metallurgy
Q1 — Diborane: Preparation, Structure & Bonding
Q1. Write a brief note on the preparation, structure, and bonding of diborane (B2H6). (6 marks)
Answer:
Diborane can be prepared by reducing boron trifluoride (BF3) with lithium aluminium hydride or by reacting sodium borohydride (NaBH4) with acids. The molecule consists of two boron atoms linked to four terminal hydrogen atoms and two bridging hydrogen atoms. The four terminal B–H bonds
Essential Chemistry Principles and Atomic Theory
1. Mathematics and Measurement in Chemistry
- Chemistry utilizes mathematics for measuring, calculating, and comparing data.
- It relies on SI Units (grams, liters, meters, Kelvin, etc.).
- Unit conversions are common (e.g., grams to kilograms).
- Accuracy and precision are critical in all experimental procedures.
Example: Measuring 25.0 mL of water provides precise data.
2. The Scientific Method and Data Analysis
- Steps: Ask a question → Form a hypothesis → Experiment → Collect data → Analyze → Conclude.
Understanding Coffee Brewing: Key Concepts and Techniques
1) Sensory Scoring Criteria
| Category | Focus | Sensory Indicators |
|---|---|---|
| Fragrance/Aroma | Smell before & after brewing | Floral, nutty, chocolatey, smoky; light roasts have brighter/fruitier notes, dark roasts are more smoky. |
| Flavor | Overall taste profile | Sweet, bitter, sour, complex |
| Aftertaste | Finish or lingering taste | Clean, smooth, or harsh |
| Acidity | Brightness, liveliness | Citrus, apple, wine-like |
| Body | Mouthfeel or texture | Light, medium, heavy |
| Balance | Harmony among traits | Well-rounded, even |
| Sweetness | Smoothness & pleasantness | Honey, |
Biology and Physics Concepts: Cell Structure to Forces
Characteristics of Living Organisms (MRS. GREN)
- Movement (change position)
- Respiration (convert nutrients) 呼吸
- Sensitivity (sense) 敏感
- Growth (permanent increase)
- Reproduction (gametes, fertilisation) 繁殖
- Excretion (waste products removed) 排泄
- Nutrition (taking of nutrients into the body)
Cell Structure
Animal Cells
- Cytoplasm: The jelly-like substance filling the cell.
- Cell Membrane: Controls substances entering and leaving the cell.
- Nucleus: Contains genetic material that controls how a cell grows
Ionic, Covalent, and Metallic Bonds: Properties and Formation
Ionic Bonds: Formation and Properties
An ionic bond is a chemical link formed between a metal and a non-metal. This typically involves elements from groups such as:
- Group IA: Alkali Metals
- Group IIA: Alkaline Earth Metals
- Group VIA: Chalcogens
- Group VIIA: Halogens
Characteristics of Ionic Compounds
- High Melting and Boiling Points: The ionic bond is very strong. A significant amount of energy is required to overcome the electrostatic forces of attraction between the ions in the crystal lattice.
- Hard but