Chemistry Questions for SSC MTS

Atomic Structure and Periodic Table

Atoms are made of protons (positive), neutrons (neutral), and electrons (negative). The periodic table arranges elements by atomic number. Periods are horizontal rows (increase in electron shells), and groups are vertical columns (similar chemical properties). For SSC MTS, you need to know the position of common elements and basic trends: metallic character decreases left to right in a period, and increases down a group.

• Atomic number = number of protons (defines the element)
• Mass number = protons + neutrons
• Valency = number of electrons in outermost shell (or 8 minus that number)
• Metals are on the left and center of periodic table; nonmetals on the right
• Noble gases (Group 18) have full outer shells and are unreactive
• Alkali metals (Group 1) are highly reactive and soft

Acids, Bases, and pH

Acids taste sour, turn blue litmus red, and have pH less than 7. Bases taste bitter, turn red litmus blue, and have pH greater than 7. pH scale runs from 0 to 14; pH 7 is neutral (pure water). Common acids: hydrochloric acid (HCl), sulfuric acid (H2SO4), acetic acid (vinegar). Common bases: sodium hydroxide (NaOH), ammonia (NH3). When an acid and base react, they neutralize each other to form salt and water.

• pH less than 7 = acidic; pH greater than 7 = basic; pH = 7 is neutral
• Stronger acids: HCl, H2SO4, HNO3
• Stronger bases: NaOH, KOH, Ca(OH)2
• Acid + Base → Salt + Water (neutralization reaction)
• Litmus paper: red in acid, blue in base
• Universal indicator shows exact pH value with color change

Metals and Nonmetals

Metals are shiny, conduct electricity and heat, are malleable (can be beaten into sheets), and ductile (can be drawn into wires). They lose electrons to form positive ions. Nonmetals are dull, poor conductors, and brittle. They gain electrons to form negative ions. Metalloids (like silicon, arsenic) have properties between metals and nonmetals. Common metals: iron, copper, aluminum, gold. Common nonmetals: oxygen, nitrogen, sulfur, chlorine.

• Metals: shiny, malleable, ductile, conduct heat and electricity
• Nonmetals: dull, brittle, poor conductors
• Metals lose electrons (form cations); nonmetals gain electrons (form anions)
• Reactivity of metals: alkali metals most reactive, noble metals least reactive
• Corrosion: metals react with oxygen and moisture (e.g., rusting of iron)
• Alloys: mixtures of metals (e.g., brass = copper + zinc, steel = iron + carbon)

Chemical Reactions and Combustion

A chemical reaction is a process where substances (reactants) transform into new substances (products). Combustion is a reaction with oxygen that releases heat and light. Complete combustion produces carbon dioxide and water; incomplete combustion produces carbon monoxide (poisonous). Oxidation is loss of electrons; reduction is gain of electrons. Rusting is slow oxidation of iron in presence of oxygen and moisture.

• Combustion: fuel + oxygen → carbon dioxide + water + heat
• Complete combustion: clean, blue flame; incomplete: smoky, yellow flame
• Rusting: 4Fe + 3O2 + 6H2O → 4Fe(OH)3 (requires oxygen and moisture)
• Prevention of rusting: painting, oiling, galvanization, alloying
• Oxidation-reduction (redox): one substance loses electrons, another gains
• Exothermic reactions release heat; endothermic reactions absorb heat

Valency and Chemical Bonding

Valency is the combining capacity of an element. It is determined by the number of electrons in the outermost shell. Elements in the same group have the same valency. Ionic bonds form when electrons are transferred from metal to nonmetal (e.g., NaCl). Covalent bonds form when electrons are shared between nonmetals (e.g., H2O, CO2). Understanding valency helps predict chemical formulas.

• Valency = electrons in outermost shell (or 8 minus that number)
• Group 1 elements: valency 1; Group 2: valency 2; Group 13: valency 3
• Oxygen: valency 2; Nitrogen: valency 3; Chlorine: valency 1
• Ionic bond: electron transfer (metal to nonmetal); forms ions
• Covalent bond: electron sharing (usually between nonmetals)
• Formula writing: balance valencies (e.g., Na valency 1, Cl valency 1 → NaCl)

Common Compounds and Their Uses

SSC MTS tests knowledge of everyday compounds and their applications. Sodium chloride (NaCl) is table salt. Calcium carbonate (CaCO3) is limestone and chalk. Sodium bicarbonate (NaHCO3) is baking soda. Ammonia (NH3) is used in fertilizers and cleaning. Carbon dioxide (CO2) is used in fire extinguishers and carbonated drinks. Water (H2O) is the universal solvent. These compounds appear in daily life and in exam questions about practical chemistry.

• NaCl (salt): food preservation, de-icing roads, chemical industry
• CaCO3 (limestone): building material, cement, antacid
• NaHCO3 (baking soda): baking, cleaning, antacid
• NH3 (ammonia): fertilizer, cleaning agent, refrigerant
• CO2 (carbon dioxide): fire extinguishers, carbonation, plant photosynthesis
• H2O (water): solvent, coolant, essential for life

• Confusing atomic number with mass number. Atomic number is always the number of protons and defines the element. Mass number is protons plus neutrons.
• Thinking all acids are strong. Many weak acids (like acetic acid in vinegar) exist. Strength depends on degree of ionization, not concentration.
• Assuming rusting happens only with pure oxygen. Rusting requires both oxygen AND moisture. Dry oxygen alone will not cause iron to rust.
• Mixing up valency with oxidation state. Valency is combining capacity; oxidation state is the number of electrons lost or gained in a compound. For SSC MTS, focus on valency.
• Forgetting that nonmetals can form covalent bonds with each other. Students often think only metals bond with nonmetals, but CO2, H2O, and NH3 are all covalent compounds of nonmetals.

• PNEC: Protons (positive), Neutrons (neutral), Electrons (negative) — remember the charge order.
• pH 7 is neutral, below 7 is acidic (A comes before N), above 7 is basic (B comes after N).
• MNEMONIC for common strong acids: HCl, H2SO4, HNO3 — remember 'HAH' (Hydrochloric, Acid, Hydrogen).
• Metals are on the LEFT, Nonmetals on the RIGHT of the periodic table — think of a house: left side (metal frame), right side (nonmetal walls).
• RUSTING = Rust + Iron + Oxygen + Moisture — all four must be present for iron to rust.

• SSC MTS Chemistry questions rarely require calculations. Focus on definitions, properties, and practical applications. A question like 'Which of the following is a nonmetal?' is typical.
• Periodic table position questions are common. Know that metals are left/center, nonmetals are right, and noble gases are far right (Group 18).
• Expect 1-2 questions on acids and bases, often asking about pH, litmus test results, or neutralization. These are straightforward memory-based questions.
• Rusting and corrosion appear frequently. Remember: rusting requires oxygen AND moisture. Galvanization and painting are prevention methods.
• Valency questions may appear in formula-writing format. Practice writing formulas of common compounds: NaCl, CaCO3, NH3, H2SO4, NaOH. These are predictable.
• Recent papers show increased focus on everyday chemistry: uses of common compounds, safety (e.g., CO2 in fire extinguishers), and environmental chemistry (e.g., acid rain). Read questions carefully for context clues.