Everyday Chemistry
Overview
Everyday Chemistry covers chemical substances, reactions, and materials encountered in daily life. For Railway NTPC and Group D exams, questions focus on common acids, bases, salts, metals, alloys, fuels, polymers, and household chemicals. Understanding pH scale, chemical formulas, uses of common compounds, and properties of materials is essential. This chapter regularly contributes 2-4 questions per paper and is highly scoring with focused preparation.
Typed Notes
Acids, Bases & pH Scale
Acids taste sour and turn blue litmus red. Bases taste bitter and turn red litmus blue. The pH scale measures acidity or alkalinity from 0 to 14. Strong acids like H2SO4 (sulphuric acid) have very low pH. Lemon juice has pH ~2, vinegar ~3, pure water = 7, milk of magnesia ~10, and bleach ~12. Antacids like Milk of Magnesia (Mg(OH)2) neutralise excess stomach acid. Acid rain has pH below 5.6, caused by SO2 and NO2 dissolving in rainwater.
Common Salts & Household Chemicals
Table salt (NaCl) is used in food preservation. Baking soda (NaHCO3) releases CO2 when heated, making bread fluffy. Washing soda (Na2CO3·10H2O) is used as a cleaning agent. Bleaching powder is Ca(OCl)Cl — calcium hypochlorite — used for disinfecting water. Plaster of Paris is CaSO4·½H2O (calcium sulphate hemihydrate), used in making casts. Alum (KAl(SO4)2·12H2O) is used in water purification. Blue vitriol = CuSO4·5H2O; Green vitriol = FeSO4·7H2O; White vitriol = ZnSO4·7H2O.
Metals, Alloys & Corrosion
Alloys are mixtures of metals with improved properties. Brass = Copper + Zinc; Bronze = Copper + Tin; Stainless Steel = Iron + Chromium + Nickel; Solder = Lead + Tin; Duralumin = Aluminium + Copper + Magnesium + Manganese. Gold purity is measured in Carats — 24 carat is pure gold. Galvanisation coats iron with zinc to prevent rusting. Amalgam (mercury alloy) is used in dental fillings. Aluminium does not rust because it forms a protective Al2O3 layer on its surface.
Fuels, Polymers & Everyday Materials
LPG (Liquefied Petroleum Gas) mainly contains Butane and Propane; a foul-smelling gas Ethyl Mercaptan is added for leak detection. CNG (Compressed Natural Gas) is mainly Methane — cleaner fuel with less pollution. Calorific value of hydrogen is highest among fuels (~142 kJ/g). Polymers: PVC (polyvinyl chloride) for pipes; Nylon for ropes and fabrics; Teflon (PTFE) for non-stick cookware; Bakelite for electrical switches. Natural rubber is polyisoprene; vulcanisation (adding sulphur) makes it harder and more durable.
Key Concepts
Revision ke liye ek nazar — exam se pehle yahi padhna hai.
- 01pH scale ranges 0-14; pH < 7 is acidic, pH = 7 is neutral, pH > 7 is basic/alkaline; human blood pH is 7.35-7.45
- 02Common acids: HCl (hydrochloric) in stomach, H2SO4 (sulphuric) in car batteries, HNO3 (nitric) in fertilisers, CH3COOH (acetic acid) in vinegar
- 03Baking soda = NaHCO3 (sodium bicarbonate); Washing soda = Na2CO3 (sodium carbonate); Common salt = NaCl (sodium chloride)
- 04Rust formation: Iron + Oxygen + Water → Fe2O3·xH2O (hydrated iron oxide); prevented by galvanisation (zinc coating)
- 05LPG contains mainly Butane (C4H10) and Propane (C3H8); CNG is Compressed Natural Gas (mainly Methane CH4)
Questions & Solutions
Pehle khud try karo — phir solution kholo. Yahi tariqa topper banata hai.
What is the chemical formula of Baking Soda and what is its main use?
Which gas is added to LPG to detect leakage, and why?
What is galvanisation and how does it prevent rusting of iron?
Name the alloy compositions for Brass, Bronze, and Stainless Steel.
What is the pH of acid rain and what gases cause it?
Everyday Chemistry for Railway exams focuses on pH scale, common acids and bases, household chemicals with their formulas, alloys and their compositions, corrosion prevention, fuels like LPG and CNG, and common polymers. Memorising chemical names, formulas, and uses of substances like baking soda, washing soda, bleaching powder, and Plaster of Paris is critical for scoring well in this chapter.
Chapter-end quiz
4 MCQsOption tap karo — turant pata chalega sahi ya galat, explanation ke saath.
Q1.Which of the following is the chemical name of 'Plaster of Paris'?
Q2.The calorific value is HIGHEST for which fuel?
Q3.Which metal forms a protective oxide layer on its surface, preventing further corrosion?
Q4.Blue Vitriol is the common name for which chemical compound?
Mark karo — dashboard par progress dikhega.