Maharashtra State Board · Class 10 · All chapters

Chemistry — Complete Formula Sheet

Board Formulas

66 formulas · 6 chapters

Ch 2 · Introduction to Matter — Mole Concept and Chemical Calculations

1.Mole from Mass★
$n = \frac{m}{M}$
$n$ : Number of moles (mol) · $m$ : Mass of substance (g) · $M$ : Molar mass (g/mol)
Number of moles = given mass ÷ molar mass. Cornerstone of every stoichiometry problem.
2.Number of Particles★
$N = n \times N_{A}$
$N_{A}$ : Avogadro's number = 6.022 × 10^23 per mol
Total particles = moles × Avogadro's number. Works for atoms, molecules, ions.
3.Avogadro's Number
$N_{A} = 6.022 \times 1 0^{23} mol^{- 1}$
Number of particles present in 1 mole of any substance.
4.Molar Volume at STP
$V_{m} = 22.4 L/mol at STP$
1 mole of any ideal gas occupies 22.4 L at STP (0 °C, 1 atm).
5.Mass Percentage★
$% w / w = \frac{m _{so l u t e}}{m _{so l u t i o n}} \times 100$
Solution mass = solute + solvent. Fraction of solute in total solution mass.
6.Volume Percentage
$% v / v = \frac{V _{so l u t e}}{V _{so l u t i o n}} \times 100$
Common for liquid-in-liquid solutions such as alcohol content.
7.Percentage Composition
$% element = \frac{n \times atomic mass}{M _{co m p o u n d}} \times 100$
n = number of atoms of that element in one molecule. All %s must sum to 100.
8.Empirical Formula Ratio
$ratio = \frac{% mass}{atomic mass}$
Divide each by smallest, then round or multiply to whole numbers.
9.Molecular Formula from Empirical
$Mol. = n \times Emp., n = \frac{M _{m o l}}{M _{e m p}}$
n must be a positive integer (usually 1, 2 or 3).

Ch 2 · Periodic Classification of Elements

1.Dobereiner's Law of Triads
$Atomic mass of middle \approx \frac{m _{1} + m _{3}}{2}$
$m_{1}, m_{3}$ : Atomic masses of first and third elements
Triad = three elements with similar chemistry. Example: Li(7), Na(23), K(39) — (7+39)/2 = 23.
2.Newlands' Law of Octaves
$Property of n^{th} element \approx (n + 8)^{th}$
Every 8th element resembled the first, like musical octaves. Failed beyond Ca.
3.Mendeleev's Periodic Law★
$Properties = f (atomic mass)$
Properties of elements are a periodic function of their atomic mass.
4.Modern Periodic Law (Moseley, 1913)★
$Properties = f (atomic number Z)$
Properties are a periodic function of Z. Resolves Ar-K and Co-Ni anomalies.
5.Maximum Electrons in Shell (Bohr-Bury)
$Max = 2 n^{2}$
n = 1 → 2 e-, n = 2 → 8 e-, n = 3 → 18 e-, n = 4 → 32 e-.
6.Valency Rule★
$Valency = ve if ve \leq 4; Valency = 8 - ve if ve > 4$
Group 18 valency = 0 (already stable octet). ve = valence electrons.
7.Atomic Radius Trend★
$Across period ↓; Down group ↑$
Effective nuclear charge pulls e- inward across a period; adding a shell increases size down a group.
8.Electronegativity Trend
$Across period ↑; Down group ↓$
F is most electronegative (3.98 Pauling). Metallic character shows the opposite trend.
9.Ionisation Energy Trend
$Across period ↑; Down group ↓$
Energy to remove outermost e-. Highest for noble gases, lowest for alkali metals.
10.Atomic Number and Mass Number
$A = Z + N$
A = mass number, Z = number of protons (= atomic number), N = number of neutrons.

Ch 3 · Chemical Reactions and Equations

1.Law of Conservation of Mass
$Mass of reactants = Mass of products$
Every balanced equation obeys this law — total atoms of each element are equal on both sides.
2.Combination Reaction★
$A + B \to A B$
Two or more reactants combine to form a single product. Example: 2Mg + O_2 → 2MgO.
3.Decomposition Reaction★
$A B \to A + B$
One reactant breaks down. Types: thermal (Δ), electrolytic (electric), photochemical (light).
4.Displacement Reaction
$A + B C \to A C + B$
More reactive metal displaces less reactive one. Zn + CuSO_4 → ZnSO_4 + Cu.
5.Double Displacement
$A B + C D \to A D + C B$
Two salt solutions exchange partners. Often produces a precipitate or gas.
6.Precipitation Example
$B a C l_{2} + N a_{2} S O_{4} \to B a S O_{4} ↓ + 2 N a C l$
White precipitate of barium sulphate — a classic double-displacement (precipitation) test.
7.Thermal Decomposition of Calcium Carbonate
$C a C O_{3} Δ C a O + C O_{2} ↑$
Basis of lime production. CaO = quicklime.
8.Electrolysis of Water
$2 H_{2} O electricity 2 H_{2} ↑ + O_{2} ↑$
Volume ratio at cathode : anode = 2 : 1 (H_2 : O_2).
9.Photodecomposition of Silver Chloride
$2 A g C l light 2 A g + C l_{2}$
White AgCl turns greyish — basis of black-and-white photography.
10.Thermite Reaction (Redox)★
$F e_{2} O_{3} + 2 A l \to 2 F e + A l_{2} O_{3} + heat$
Highly exothermic — molten Fe used to weld broken rails.
11.Oxidation and Reduction
$Oxidation: loss of electrons; Reduction: gain of electrons$
OIL RIG — Oxidation Is Loss, Reduction Is Gain.
12.Photosynthesis (Endothermic)
$6 C O_{2} + 6 H_{2} O sunlight C_{6} H_{12} O_{6} + 6 O_{2}$
Energy from sunlight is absorbed — an endothermic reaction.

Ch 5 · Acids, Bases and Salts

1.Ionisation of an Acid
$H C l \to H^{+} + C l^{-}$
Acid releases H+ ions in aqueous solution (Arrhenius). Strong acid ionises completely.
2.Ionisation of a Base
$N a O H \to N a^{+} + O H^{-}$
Base releases OH- ions in aqueous solution.
3.Neutralisation Reaction★
$Acid + Base \to Salt + Water$
H+ from acid combines with OH- from base to give water; remaining ions form the salt. Exothermic.
4.Definition of pH★
$p H = - lo g_{10} [H^{+}]$
$[H^{+}]$ : Molar concentration of H+ ions (mol/L)
Negative logarithm of H+ concentration in mol/L. Range 0-14.
5.pOH and its Relation
$pO H = - lo g_{10} [O H^{-}], p H + pO H = 14$
At 25 °C the sum is always 14 for aqueous solutions.
6.Ionic Product of Water
$K_{w} = [H^{+}] [O H^{-}] = 1 0^{- 14} at 25 ° C$
In pure water [H+] = [OH-] = 10^-7 mol/L, giving pH = 7.
7.Acid + Metal
$Z n + 2 H C l \to Z n C l_{2} + H_{2} ↑$
Metals above H in activity series displace H_2. Test: burning splinter gives 'pop'.
8.Acid + Metal Carbonate
$2 H C l + N a_{2} C O_{3} \to 2 N a C l + H_{2} O + C O_{2} ↑$
CO_2 evolved turns lime water milky — a standard SSC identification.
9.Chlor-alkali Process★
$2 N a C l (a q) + 2 H_{2} O electrolysis 2 N a O H + C l_{2} ↑ + H_{2} ↑$
Three products: NaOH (solution), Cl_2 (anode), H_2 (cathode). Basis of soaps, PVC, bleaches.
10.Formation of Baking Soda (Solvay first step)
$N a C l + H_{2} O + C O_{2} + N H_{3} \to N H_{4} C l + N a H C O_{3}$
NaHCO_3 = baking soda (Marathi: खाण्याचा सोडा).
11.Formation of Washing Soda
$2 N a H C O_{3} Δ N a_{2} C O_{3} + H_{2} O + C O_{2}$
Heating baking soda and then recrystallising with 10 waters gives washing soda Na_2CO_3·10H_2O.
12.Bleaching Powder
$C a (O H)_{2} + C l_{2} \to C a O C l_{2} + H_{2} O$
Dry slaked lime + chlorine → bleaching powder. Used as disinfectant and bleach.

Ch 8 · Metallurgy — Metals and Non-metals

1.Reactivity Series (Descending)★
$K > N a > C a > M g > A l > Z n > F e > P b > H > C u > H g > A g > A u$
Above H → displaces H from acid. Below H → does not react with dilute HCl/H_2SO_4.
2.Formation of Ionic Bond
$N a + C l \to N a^{+} + C l^{-} \to N a C l$
Metal loses e-, non-metal gains e-, ions attract electrostatically.
3.Metal + Oxygen
$4 N a + O_{2} \to 2 N a_{2} O$
Metals form basic oxides. Na burns vigorously; Fe rusts slowly.
4.Metal + Acid★
$Metal + 2 H C l \to Metal chloride + H_{2} ↑$
Only metals above H in the activity series react. Cu, Ag, Au do not.
5.Metal Displacement in Solution
$F e + C u S O_{4} \to F e S O_{4} + C u$
Blue colour of CuSO_4 fades, brown Cu deposits on iron nail (Fe > Cu).
6.Roasting (Sulphide Ore)★
$2 Z n S + 3 O_{2} Δ 2 Z n O + 2 S O_{2}$
Sulphide ore heated in EXCESS air → metal oxide + SO_2. Used for Zn, Cu, Pb ores.
7.Calcination (Carbonate Ore)
$Z n C O_{3} Δ Z n O + C O_{2}$
Carbonate ore heated in LIMITED air → metal oxide + CO_2. Used for calamine, malachite.
8.Reduction of Oxide by Carbon
$Z n O + C Δ Z n + C O$
Middle-of-series metals (Zn, Fe, Pb) — cheap carbon reduction from coke.
9.Electrolytic Reduction (for K, Na, Ca, Mg, Al)
$At cathode: M^{n +} + n e^{-} \to M$
Molten metal chloride/oxide is electrolysed. Al from molten Al_2O_3 in cryolite (Hall-Héroult).
10.Rusting of Iron
$4 F e + 3 O_{2} + x H_{2} O \to 2 F e_{2} O_{3} \cdot x H_{2} O$
Both O_2 and H_2O required. Prevented by galvanising, painting, oiling, alloying.
11.Amphoteric Oxide (Al_2O_3)
$A l_{2} O_{3} + 6 H C l \to 2 A l C l_{3} + 3 H_{2} O; A l_{2} O_{3} + 2 N a O H \to 2 N a A l O_{2} + H_{2} O$
Reacts with both acid and base — the definition of amphoteric. Also true for ZnO.
12.Thermite Reaction★
$F e_{2} O_{3} + 2 A l \to 2 F e + A l_{2} O_{3} + heat$
Highly exothermic; molten iron used to weld broken railway tracks.

Ch 9 · Carbon and Its Compounds

1.General Formula of Alkanes★
$C_{n} H_{2 n + 2}$
$n$ : Number of carbon atoms (n = 1, 2, 3, ...)
Saturated hydrocarbons — only single C-C bonds. Methane, ethane, propane, butane.
2.General Formula of Alkenes★
$C_{n} H_{2 n}$
One C=C double bond. Ethene (C_2H_4), propene, but-1-ene.
3.General Formula of Alkynes
$C_{n} H_{2 n - 2}$
One C≡C triple bond. Ethyne (acetylene, C_2H_2).
4.Combustion of Methane
$C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O + heat$
Complete combustion gives CO_2 and water; a blue flame indicates enough O_2.
5.General Combustion of Alkane
$C_{n} H_{2 n + 2} + (\frac{3 n + 1}{2}) O_{2} \to n C O_{2} + (n + 1) H_{2} O$
Substitute n to get the equation for methane, ethane, etc.
6.Addition (Hydrogenation)★
$C H_{2} = C H_{2} + H_{2} Ni C H_{3} - C H_{3}$
Ni catalyst adds H_2 across double bond — converts unsaturated to saturated. Basis of vanaspati manufacture.
7.Substitution (Chlorination of Methane)
$C H_{4} + C l_{2} sunlight C H_{3} C l + H C l$
One H replaced by Cl. Free-radical substitution — characteristic of alkanes.
8.Oxidation of Ethanol to Ethanoic Acid
$C H_{3} C H_{2} O H alk. KMnO_{4} Δ C H_{3} C O O H$
Alkaline KMnO_4 or acidified K_2Cr_2O_7 oxidises the -OH to -COOH.
9.Ester Formation (Esterification)★
$C H_{3} C O O H + C H_{3} C H_{2} O H conc. H_{2} SO_{4} C H_{3} C O O C_{2} H_{5} + H_{2} O$
Sweet-smelling ester — used in perfumes and flavours. Acid catalyst is conc. H_2SO_4.
10.Saponification (Soap Making)
$Fat/Oil + 3 N a O H \to Soap + Glycerol$
Alkaline hydrolysis of triester. Sodium salt of long-chain fatty acid = soap.
11.Reaction of Sodium with Ethanol
$2 C H_{3} C H_{2} O H + 2 N a \to 2 C H_{3} C H_{2} O N a + H_{2} ↑$
Distinguishes -OH group from ether — produces H_2 gas.