10th Science Most Important Repeated Concepts
𝗣𝗮𝘀𝘀𝗶𝗻𝗴 𝗣𝗮𝗰𝗸𝗮𝗴𝗲
𝗖𝗵𝗲𝗺𝗶𝘀𝘁𝗿𝘆
CHEMICAL REACTIONS AND EQUATIONS
→Chemical reaction
★ Reactant converted into product.
→ Changes in chemical reactions
★ Change in colour
★ Change in temperature
★ Change in state
★ Evolution of gas
→Chemical equation
★ Symbolically representation of chemical reaction.
→Balanced chemical equation
★ Same number of atoms in LHS and RHS
★ To follows the law of conservation of mass
Important balanced Chemical equations
★ Hydrogen + Chlorine → Hydrogen chloride
H2 + Cl2 → 2HCl
★ Sodium + Water → Sodium hydroxide + Hydrogen.
2Na(s) + 2H2O(l) → 2NaOH(aq) +H2(g)
★ lead nitrate is heated.
2Pb(NO3)2 →2PbO + 4NO2 + O2
★ Calcium oxide reacts with water to form slaked lime
CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat
★ Burning of natural gas
CH4+ 2O2 → CO2 + 2H2O
★ Calcium carbonate → Calcium oxide + Carbon dioxide, (Lime stone on heating)
CaCO3 → CaO + CO2
★ Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen.
Mg + HCl → MgCl2 + H2
★ Sodium sulphate reacts with Barium chloride
Na2SO4 + BaCl2 → BaSO4 + 2NaCl
★ Reaction of Barium chloride with Aluminium sulphate
BaCl2 + Al2( SO4)3 → 3BaSO4 + 2AlCl3
★ Reaction of lead with Copper Chloride
Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s)
★ heating of ferrous sulphate crystals.
2FeSO4(s) → Fe2O3(s)+SO2(g)+SO3(g)
★ Zinc reacts with copper sulphate solution.
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
★ Zinc carbonate (s) → Zinc oxide (s)+ Carbon dioxid
ZnCO3(s) → ZnO(s) + CO2(g)
★ Silver chloride exposed to the sunlight.
AgCl2 → Ag + Cl2
★ H2 + O2 → H2O
2H2 + O2 → 2H2O
★ Na2CO3 + HCl → NaCl + H2O + CO2
Na2CO3 + 2HCl → 2NaCl + H2O + CO2
★ N2 + H2 → NH3
N2 + 3H2→ 2NH3
★ NaCl + AgNO3 → AgCl + NaNO3
NaCl + AgNO3 → AgCl + NaNO3
→ Combination reactions
Two reactants →one product
Ex:
➤ CaO + H2O → Ca(OH)2 + Heat
(Quick lime) (Slaked lime)
➤ Burning of coal: C + O2 → CO2
➤ Formation of water: 2H2 + O2→ 2H2O(l)
→ Decomposition reaction
One reactant → two or more products
→ Thermal decomposition
➤ 2FeSO4 → Fe2O3 + SO2 + SO3
lose water when heated and the colour of the crystals changes.
➤ CaCO3 → CaO + CO2
Calcium oxide in the manufacture of cement.
➤ 2Pb(NO3)2 → 2PbO + 4NO2 + O2
Emission of brown fumes are of nitrogen dioxide (NO2).
→ Electrolytic decomposition (Electrolysis of water)
2H2O → 2H2 + O2
★ Cathode - H2
★ Anode - O2
→ Photolytic decomposition
Ex:
➤ 2AgCl → 2Ag + Cl2
white silver chloride turns grey in sunlight. This is due to the decomposition of silver chloride into silver and chlorine by light.
➤ 2AgBr → 2Ag + Br2
above reactions are used in black and white photography.
→ Oxidation
★ Addition of oxygen
Ex:
➤ 2Cu + O2 → 2CuO
➤ 2Zn + O2 → 2ZnO
→ Reduction
★ Removing of oxygen
Ex: ZnO + C →Zn + CO
→ Redox reaction
★ Oxidation and reduction occur in same reaction.
Ex: CuO + H2 → Cu + H2O
→ Displacement reaction
★ More reactive element displace the less reactive element.
Ex:
➤ Fe + CuSO4 → FeSO4
Iron replace the copper form copper sulphate, iron more reactive than copper.
➤ Fe2O3 + 2Al → Al2O3 + 2Fe
→ Double displacement reaction
★ Exchange of ions between reactants.
Ex: Na2SO4 + BaCl2 → BaSO4 + 2NaCl
→ Precipitation reaction
★ Insoluble substance formed in the reaction
Ex: Na2SO4 + BaCl2 → BaSO4 + 2NaCl
Precipitate - BaSO4
Ions - Ba^2+ and SO4 ^ 2-
→ Exothermic reaction
Heat released in the reaction
Ex:
➤ CaO + H2O → Ca(OH)2 + Heat
➤ Burning of natural gas -
CH4 + 2O2 → CO2 + 2H2O
→ Endothermic Reaction
Heat absorbed in the reaction
Ex: CaCO3 →CaO + CO2
→ Corrosion
★ Metal + atmosphere substance → Undesirable substance
Ex: Rusting of iron
→ Rancidity
★ Smell /taste of oil/fat containing substance change by oxidation.
Prevention
★ Use Antioxidant
★ Refrigerating.
★ Use Nitrogen gas
★ Pack in air tight container
→ Important Oxidised and Reduced reactants.
★ Na + O2 →Na2O
Oxidized substance - Na
Reduced substance - O2
★ CuO + H2 → Cu + H2O
Oxidized substance - H2
Reduced substance - CuO
★ ZnO + C → Zn + CO
Oxidized substance - C
Reduced substance - ZnO
ACIDS, BASES AND SALTS
→ Acid.
★ Sour taste
★ Produce H+ ions
★ Blue litmus to red
★ pH below 7
★ Ex: HCl, H2SO4
→Base
★ Bitter taste
★ Produce OH- Ions
★ Red litmus to blue
★ pH above 7
★ Ex: NaOH, KOH, Ca(OH)2...
→Reactions
★ Acid + Metal → Salt + Hydrogen gas
Ex: H2SO4 + Zn → ZnSO4 + H2
★ Acid + Metal carbonate → Salt + water + Carbon dioxide
Ex: HCl + NaHCO3 →NaCl + H2O + CO2
★ Acid + Metal oxide → Salt + Water
2HCl + ZnO →ZnCl2 + H2O
Neutralization reaction
★ Acid + Base →Salt + Water
Ex: NaOH + HCl →NaCl + H2O
→ Some naturally occurring acids
★ Vinegar - Acetic acid
★ Orange - Citric acid
★ Tamarind - Tartaric acid
★ Tomato - Oxalic acid
★ Sour milk (Curd) - Lactic acid
★ Nettle sting - Methanoic acid
★ Ant sting - Methanoic acid
★ Lemon - Citric acid
→Tooth decay
Causes
★ In our mouth, bacteria convert sugar into acid
★ This acid cause tooth decay
Prevention
★ Use toothpaste which is basic and it neutralize the acid
Blood pH: 7.2 to 7.8
Acid rain pH: below 5.6
concentrated acid: Acid with more concentration of H+ (or) larger amount of acid in less amount of water
Dilute acid: Acid with less concentration of H+ (or) less amount of acid in larger amount of water.
Strong acid: completely dissolve in water
Weak acid: incompletely dissolve in water
→ Chloro alkali process
2NaCl + 2H2O→ 2NaOH + Cl2 + H2
Product uses:
NaOH
★ Soaps and detergents
★ Papar making
Cl2
★ Water treatment
★ Swimming pool
★ PVC
H2
★ Fuels
★ Margarine
Brine solution: Aqueous solution of sodium chloride
→ Washing Soda
★ Chemical name - Sodium carbonate
★ Chemical formula -Na2CO3
Uses
★ Manufacture of borax,
★ softening of hard water
→Baking Soda
★ Chemical name - Sodium hydrogen carbonate
★ Chemical formula -NaHCO3
Uses -
★ antacid
★ ingredient of baking powder
→ Bleaching Powder
★ Chemical name - Calcium oxychloride
★ Chemical formula -CaOCI2
Uses -
★ Bleaching clothes
★ oxidizing agents
★ disinfecting water
→ Plaster of Paris
★ Chemical name - Calcium sulphate Hemihydrate
★ Chemical formula -CaSO4.1/2H2O
Uses -
★ Fractured bones
★ Making toys
★ Decorative materials
➤ water of crystallisation: fixed number of water molecules present in one formula unit of a salt.
Ex: CuSO4.5H2O, here W.C. is 5
➤ chemical name and formula of Marble and limestone is calcium carbonate - CaCO3
➤ Farmer treat the soil of his field with slaked lime When acidic property of soil increases
𝗠𝗲𝘁𝗮𝗹𝘀 𝗮𝗻𝗱 𝗡𝗼𝗻-𝗠𝗲𝘁𝗮𝗹𝘀
→ Physical properties of Metals
★ Sonorous
★ Ductile
★ Lustrous
★ Conduct heat and electricity
→ Physical Properties of Non-Metals
★ No sonorous
★ No ductile
★ No malleable
★ Poor conductor of electricity
Ductile : Metal can drawn in to thin wire.
Malleable : Metal can beaten in to thin sheet.
→ Chemical properties of metals :
★ Liberates H2 from dilute acids.
★ Metallic oxides are basic in nature.
→ Chemical properties of non-metals :
★ Do not liberate H2 from dilute acids.
★ Oxides of non-metals are acidic in nature.
→ Formation of NaCl
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