1. The more electropositive metals displace less electropositive metals from their compounds in aqueous solution.
Take some dilute CuSO4 solution in a test tube, and introduce a piece of Zn or iron in it. Zn or Fe gradually displaces copper from copper sulphate solution. Copper metal is thrown out of the solution and is plated on the zinc or iron metal.
Zn + CuSO4 ————> ZnSO4 + Cu
Similarly, Fe + CuSO4 ———–> ?
Cu + AgNO3 ————> ?
2. Metals above hydrogen in the electrochemical series displace H2 gas from non-oxidizing acids (dil. HCL or dil H₂SO4).
Put a piece of Zn metal in some dil H₂SO4 in a test tube. Zn displaces H₂ gas from H₂SO4 and hydrogen gas bubbles out.
Zn + H₂SO4 —————> ZnSO4 + H₂
Similarly, Fe + HCL ——-> ?
Mg + H₂SO4 ———> ?
Examples under (1) and (2) are displacement reactions.
3. Alkali metals (Li, Na K, Rb, Cs) and alkaline earth metals (Ca, Sr, Ba) displace hydrogen gas from cold water.
Take some water in a small beaker, and drop a piece of sodium on it. Sodium darts on the surface of water like a hovercraft, and displaces hydrogen from water. Put a drop of phenolphthalein in the solution when it turns pink.
2Na+ 2HOH ————> 2NaOH + H₂
Similarly, K + HOH ————-> ?
Ca+HOH————? ?
4. Electropositive metals directly combine with the electronegative non metals to form their corresponding compounds.
Take a little quantity of the mixture of iron filings and sulphur powder in a dry test tube, and heat for some time.
The mixture glows red hot with the formation of ferrous sulphide (FeS) and evolution of a large quantity of energy.
It is an exothermic reaction.
Fe + S————->FeS + heat
Similarly Zn + S———-> ?
2Na+ Cl₂ ———> ?
These are the examples of synthesis reactions.
5. Acid + base —————> Salt + Water.
Acids and bases neutralize each other to form salt and water.
Take a little dil NaOH solution in a test tube, and add a drop of phenolphthalein. Now add dil HCl from a glass tube till the pink color Just vanishes.
It shows that the alkali is neutralized by the acid.
NaOH + HCl—————> NaCl + H₂O
Similarly, KOH + H₂SO4 ———-> ?
LiOH + HNO3————–> ?
These are neutralization reactions.
6. More electronegative non metals displace less electronegative non metals from their binary salts.
i) Take a little KI solution and a few drops of chloroform in a test tube. Add 2-3 drops of bromine water in It. Shake well. The bottom layer of chloroform is coloured violet due to the liberation of free iodine. Bromine liberates iodine from KI.
Br₂ + 2KI—————> 2KBr + I₂
ii) Take a little KBr solution + a few drops of chloroform in a test tube. Add 2-3 drops of chlorine water or (if chlorine water is not available, add 1 crystal of KMnO4 and then 1- 2 ml of Conc. HCI). Shake well, and allow it to settle. The bottom layer of chloroform is coloured brown due to the liberation of free bromine.
Cl₂ + 2KBr————-> 2KCI+ Br₂
Similarly, F₂ + KCl ——–> ?
F₂ + NaI ——-> ?
F₂ + NaBr——-> ?
F₂ > Cl₂> Br₂ > I2 (in electronegativity)
7. Most metallic hydroxides (except alkali metal hydroxides and alkaline earth metal hydroxides) decompose on heating to give corresponding oxide and water vapour.
Take some copper hydroxide in a dry test tube, and heat it strongly in the Bunsen flame.
The residue left on the test tube is black. It is the black oxide of copper (CuO). Moisture deposits on the upper part of the test tube. Bring a few particles of anhydrous CuSO4 in contact with the drops of moisture deposited. The anhydrous CuSO4 turns blue. It shows that the drops of liquid deposited are water drops.
Cu(OH)₂ ————-> CuO + H₂O
Similarly, Mg(OH)₂ ————> ?
Zn(OH)₂ ————> ?
8. Most metallic carbonates (except alkali metal carbonates) decompose on heating to form corresponding oxide and carbon dioxide.
Take some CaCO3 or MgCO3 powder in a dry test tube and heat it strongly, and pass the issuing gas through some lime water taken in another test tube as shown in fig 3.1
The lime water turns milky. showing that the gas coming out is carbon dioxide.
CaCO3 —————> CaO + CO2↑
Similarly, MgCO3 ————-> ?
9. Most heavy metal nitrates decompose on heating to give oxide, brown nitrogen dioxide and oxygen.
Take a little Cu(NO3)2 crystals in a dry test tube and heat it strongly.
Brown fumes are evolved, and the residue left is black.
2Cu(NO3)2 —————> 2 CuO + 4NO₂ + O₂
Similarly Mg(NO3)2 —————> ?
Ca(NO3)2 —————-> ?
Co(NO3)2 —————-> ?
The reactions under 7,8,9 are the examples of thermal decomposition brought about by the action heat.
10. All carbonates are decomposed by dilute mineral acids to form salt, carbon dioxide and water.
Take some marble pieces (CaCO3) in a test tube, and add dilute HCL, when effervescence takes place. Pass the issuing gas through some lime water taken in another test tube as in fig. 3.1. Also see what happens when excess gas is passed for some time more.
First, the lime water turns milky. When the gas is passed in excess, the milky white ppt. disappears to form a clear solution.
CaCO3 + 2HCI————> CaCl₂ + CO₂ + H₂O
Ca(OH)₂ + CO₂ ————> CaCO3↓ + H₂O
milky
CaCO3 + H₂O + CO₂—————> Ca(HCO3)₂
excess
Similarly, MgCO3 + HCL ————–> ?
ZnCO3 + HCI————–?
11. All bicarbonates are decomposed by dil acids to form salt, carbon dioxide and water.
Take some sodium bicarbonate in a dry test tube, and add dilute HCl or dil H₂SO4, and pass the issuing gas through some lime water taken in another test tube.
Effervescence occurs, and the lime water turns milky.
NaHCO3 + HCl————> NaCl + CO₂ + H₂O
Similarly, NaHCO3 + H₂SO4 ———> ?
Mg(HCO3)₂ + HCI ———–>?
Ca(HCO3)₂ + HNO3 ———-> ?
12. All sulphites are decomposed by dil mineral acids to give salts, sulphur dioxide and water.
Take some sodium sulphite in a dry test tube, and add dil HCl or H2SO4, and test the gas evolved with an acidified pot. permanganate paper.
Effervescence occurs. The gas evolved has the smell of burning sulphur, and decolourises the pink colour of acidified KMnO4.
Na2SO3 + H₂SO4 ————-> Na₂SO4 + SO₂ + H₂O
Similarly K2SO3 + HCI ——-> ?
CaSO3 + HNO3 ——–> ?
13. All bisulphites are decomposed by mineral acids to form salt, sulphur dioxide and water.
Take some sodium bisulphite in a dry test tube, and add dil HCI or H₂SO4, and test the gas evolved with an acidified pot. Permanganate paper.
Observation as in No. 12
NaHSO3 + HCl ———–> NaCl + H₂O + SO₂
Similarly, KHSO3 + H₂SO4 ———-> ?
Ca(HSO3)2 + HNO3 ——— ?
The reactions under 10, 11, 12, 13 are the examples of decomposition of salts by the action of acids.
14. Most metallic oxides are basic oxides, and most non metallic oxides are acidic oxides.
Repeat Expt. No. 8, and pass the issuing CO₂ gas through some water taken in another test tube. Allow the heated test tube to cool down. Add water to it and shake well to form milk of lime.
Now, test both the milk of lime and carbon dioxide water with litmus papers.
The milk of lime turns red litmus into blue. The CO₂ water turns blue litmus into red.
It shows that milk of lime is basic, and the CO₂ water is acidic.
CaO +H2O ———–> Ca(OH), (basic)
CO₂ + H₂O————> H₂CO3 (Acidic)
Carbonic acid
Similarly
Na₂O + H₂O ———-> ?
MgO + H₂O ————> ?
BaO + H2O —————> ?
SO₂ + H₂O —————-> ?
SO3 + H₂O —————-> ?
N₂O5 + H₂O ————–> ?