Telangana PSC – General Awareness & Current Affairs
Topic: Chemistry Basics
A quick, concise guide to the fundamentals of chemistry that you can use for exam revision, interview questions or general knowledge.
1. Simple Explanation
Chemistry is the science of matter, its properties, how it changes, and the energy associated with those changes.
- Matter: Anything that has mass and occupies space.
- Atoms: The basic building blocks of matter.
- Elements: Pure substances made of only one type of atom.
- Compounds: Substances formed when two or more different elements bond together.
- Mixtures: Physical combinations of two or more substances that can be separated by physical means.
2. Key Points
| Category | Core Idea | Important Details |
|---|---|---|
| Atoms | Structure | 1. Protons (positive) in nucleus. 2. Neutrons (neutral) in nucleus. 3. Electrons (negative) orbit around nucleus. 4. Atomic Number = protons. 5. Mass Number = protons + neutrons. |
| Elements & Periodic Table | Organization | 1. 118 elements (as of 2024). 2. Periods = rows; Groups = columns. 3. Metals, Non‑metals, Metalloids. 4. Trends: atomic radius ↑ down a group, ↓ across a period. |
| Chemical Bonding | Types | 1. Ionic (electron transfer). 2. Covalent (electron sharing). 3. Metallic (electron sea). 4. Hydrogen bond (weak, crucial in biology). |
| States of Matter | Conditions | 1. Solid – fixed shape & volume. 2. Liquid – fixed volume, adaptable shape. 3. Gas – neither fixed shape nor volume. 4. Plasma – ionized gas (stars, fluorescent tubes). |
| Reactions | Changes | 1. Combination (synthesis). 2. Decomposition. 3. Single‑replacement. 4. Double‑replacement. 5. Combustion (with O₂). |
| Stoichiometry | Quantitative analysis | 1. Use mole concept (Avogadro’s number). 2. Molar mass (g mol⁻¹).<3. Mole–mass–mass relationships. |
| Acids & Bases | pH scale | 1. Acid: pH < 7 (H⁺ donor). 2. Base: pH > 7 (OH⁻ donor). 3. Neutralization → water + salt. |
| Important Compounds | Daily relevance | 1. Water (H₂O) – universal solvent. 2. Carbon Dioxide (CO₂) – greenhouse gas. 3. Sodium Chloride (NaCl) – table salt. 4. Methane (CH₄) – natural gas. 5. Ethanol (C₂H₅OH) – fuel & solvent. |
| Industrial & Environmental Chemistry | Relevance to PSC | 1. Petrochemicals – refining crude oil to fuels. 2. Pharmaceuticals – synthesis of drugs. 3. Agriculture – fertilizers (NH₃, urea). 4. Waste Management – incineration & recycling. 5. Green Chemistry – sustainable production, biodegradable polymers. |
| Current Affairs (2024‑25) | Recent developments | 1. India’s National Chemical Laboratory announced a new biodegradable plastic patent. 2. Jain Irrigation launched a phosphate‑free fertilizer to reduce eutrophication. 3. National Hydrogen Mission – establishing a 1‑MW hydrogen plant in Telangana. 4. COVID‑19: Rapid development of mRNA vaccines (RNA‑based chemistry). |
3. Worked Example – Stoichiometry
Problem:
How many grams of sodium chloride (NaCl) are produced when 10 g of sodium (Na) reacts completely with excess chlorine (Cl₂)?
Steps
-
Write the balanced equation
[ 2,\text{Na} + \text{Cl}_2 \rightarrow 2,\text{NaCl} ] -
Find molar masses
- Na = 22.99 g mol⁻¹
- Cl₂ = 70.90 g mol⁻¹ (but excess)
- NaCl = 58.44 g mol⁻¹
-
Convert grams of Na to moles
[ n_{\text{Na}} = \frac{10,\text{g}}{22.99,\text{g mol}^{-1}} = 0.435,\text{mol} ] -
Use stoichiometry
From the equation, 2 mol Na produce 2 mol NaCl → 1 mol Na = 1 mol NaCl.
Thus, (n_{\text{NaCl}} = 0.435,\text{mol}). -
Convert moles of NaCl to grams
[ m_{\text{NaCl}} = 0.435,\text{mol} \times 58.44,\text{g mol}^{-1} = 25.4,\text{g} ]
Answer – Approximately 25.4 g of NaCl are formed.
4. Quick Revision Summary
- Atoms: protons, neutrons, electrons → atomic number