Gas evolved and test Equation 1. Oxides of potassium, sodium, calcium, magnesium, aluminum, zinc, iron and copper do not decompose on heating.

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1 1. OXIDES Name of the compound Formula Original Colour Final Colour Residue Gas evolved and test Equation 1. Oxides of potassium, sodium, calcium, magnesium, aluminum, zinc, iron and copper do not decompose on heating. 2 Zinc Oxide ZnO Yellow when hot when cold Residue turns white on cooling Does not decompose (only changes colour) Eq n : ZnO ZnO () (Yellow) 3 Lead Dioxide PbO 2 Chocolate brown Yellow Yellow residue fuses with test tube Oxygen Eq n : 2PbO 2 2PbO + O 2 4 Red Lead Pb 3 O 4 Red Yellow Yellow residue fuses with the test tube Eq n : 2Pb 3 O 4 6PbO +O 2 5 Mercuric Oxide HgO Red Silvery liquid Silvery mirror on sides of test tube 1

2 Eq n : 2HgO 2Hg + O 2 6 Silver Oxide Ag 2 O Greyish black Silver Silver residue at the bottom of the test tube Eq n : 2Ag 2 O 4Ag + O 2 2. CARBONATES GAS = PRECIPITATE = Name of the compound Formula Original Colour Final Colour Residue Gas evolved test Equation 1 Sodium and Potassium carbonate do not decompose on heating 2 Calcium Carbonate CaCO 3 residue of calcium oxide obtained Colourless, odourless, slightly acidic to litmus and turns lime water milky Eq n : CaCO 3 CaO + CO 2 3 Magnesium Carbonate MgCO 3 residue of magnesium oxide obtained Colourless, odourless, slightly acidic to litmus and turns lime water milky Eq n : MgCO 3 MgO + CO 2 2

3 4 Zinc Carbonate ZnCO 3 Yellow when hot white when cold Yellow residue of zinc oxide obtained which turns white on cooling Colourless, odourless, slightly acidic to litmus and turns lime water milky Eq n : ZnCO 3 ZnO + CO 2 5 Lead Carbonate PbCO 3 Yellow Yellow residue fuses with the sides of the test tube Colourless, odourless, slightly acidic to litmus and turns lime water milky Eq n : PbCO 3 PbO + CO 2 6 Copper Carbonate CuCO 3 Light green Black Black copper oxide formed Colourless, odourless, slightly acidic to litmus and turns lime water milky Eq n : CuCO 3 CuO + CO 2 7 Ammonium carbonate (NH 4 ) 2 CO 3 No residue Decomposes on exposure to air and leaves no residue Colourless, odourless, slightly acidic to litmus and turns lime water milky Ammonia Pungent, smelling, basic gas turns red litmus 3

4 blue and gives dense white fumes with a glass rod of HCl acid Water Vapour blue to pink Eq n : (NH 4 ) 2 CO 3 2NH 3 + H 2 O (vap) + CO 2 3. BICARBONATES Name of the compound Formula Original Colour Final Colour Residue Gas evolved test Equation 1 Sodium Bicarbonate NaHCO 3 solid sodium carbonate Colourless, odourless, slightly acidic to litmus and turns lime water milky Water Vapour blue to pink Eq n : 2NaHCO 3 Na 2 CO 3 + H 2 O +CO 2 2 Potassium Bicarbonate KHCO 3 solid potassium carbonate Colourless, odourless, slightly acidic to litmus and turns lime water milky Water Vapour 4

5 blue to pink Eq n : 2KHCO 3 K 2 CO 3 + H 2 O +CO 2 3 Calcium Bicarbonate Ca(HCO 3 ) 2 Calcium carbonate residue Colourless, odourless, slightly acidic to litmus and turns lime water milky Water Vapour blue to pink Eq n : Ca(HCO 3 ) 2 CaCO 3 + H 2 O +CO 2 Colourless, odourless, slightly acidic to litmus and turns lime water milky 4 Magnesium Bicarbonate Mg(HCO 3 ) 2 Magnesium carbonate residue Water Vapour blue to pink Eq n : Mg(HCO 3 ) 2 MgCO 3 + H 2 O + CO 2 Note: Calcium bicarbonate and Magnesium bicarbonate exists only in solution 4. NITRATES Name of the compound Original Colour Final Colour Residue Gas evolved test 5

6 Formula Equation 1 Sodium Nitrate NaNO 3 Colourless Pale yellow liquid Pale yellow liquid Eq n : 2NaNO 3 2NaNO 2 + O 2 2 Potassium Nitrate KNO 3 Colourless Pale yellow liquid Pale yellow liquid Eq n : 2KNO 3 2KNO 2 + O 2 3 Calcium Nitrate Ca(NO 3 ) 2 Colourless residue of calcium oxide Turns Potassium Iodide paper brown in colour Eq n : 2Ca(NO 3 ) 2 2CaO + 4NO 2 + O 2 4 Zinc Nitrate Zn(NO 3 ) 2 Colourless Yellow when hot white when cold residue of Zinc oxide obtained on cooling 6

7 Turns Potassium Iodide paper brown in colour Eq n : 2Zn(NO 3 ) 2 2ZnO + 4NO 2 + O 2 5 Lead Nitrate Pb(NO 3 ) 2 Yellow Yellow residue of lead monoxide fuses with the test tube Turns Potassium Iodide solution brown in colour Eq n : 2Pb(NO 3 ) 2 2PbO + 4NO 2 + O 2 6 Copper Nitrate Cu(NO 3 ) 2 Blue Black Black residue of copper oxide Turns Potassium Iodide solution brown in colour Eq n : 2Pb(NO 3 ) 2 2PbO + 4NO 2 + O 2 7 Mercuric Nitrate Hg(NO 3 ) 2 Colourless Silvery Silvery residue of mercury on the test tube 7

8 Turns Potassium Iodide paper brown in colour Eq n : Hg(NO 3 ) 2 Hg + 2NO 2 + O 2 8 Silver Nitrate AgNO 3 Colourless Silver Silvery residue of silver on the test tube Turns Potassium Iodide paper brown in colour Eq n : 2AgNO 3 2Ag + 2NO 2 + O 2 Nitrous Oxide 9 Ammonium Nitrate NH 4 NO 3 No residue Completely disappears on heating (laughing gas) Water Vapour blue to pink Eq n : NH 4 NO 3 2H 2 O + N 2 O 5. HYDROUS SALTS Name of the compound Original Final Colour Residue Gas evolved test 8

9 Formula Colour Equation A Hydrated Copper Sulphate CuSO 4 5H 2 O Blue crystalline compound anhydrous powder Greyish white residue of copper Sulphate. On strong heating the residue turns black Water vapour blue to pink Eq n : CuSO 4 5H 2 O CuSO 4 + 5H 2 O B Hydrated Sodium Carbonate Na 2 CO 3 10H 2 O crystalline solid anhydrous powder anhydrous residue of sodium carbonate Water vapour blue to pink Eq n : Na 2 CO 3 10H 2 O : Na 2 CO H 2 O 6. Other compounds a Ammonium dichromate (NH 4 ) 2 Cr 2 O 7 Orange Decomposes with sparks giving out heat and forms a green fluffy powder Green powder of chromic oxide Water vapour blue to pink Nitrogen Colourless neutral gas Eq n : (NH 4 ) 2 Cr 2 O 7 : Cr 2 O 3 + N 2 + 4H 2 O b Ammonium Chloride NH 4 Cl solid Disappears from the bottom of the test tube and settles down as a white solid on the upper cooler parts of the test tube No residue at the bottom of the test tube Ammonia Basic gas turns red litmus blue and gives dense white fumes with a glass rod dipped in HCl Hydrogen Chloride An acidic gas gives dense white fumes with a glass rod dipped in Ammonium Hydroxide Eq n : NH 4 Cl NH 3 + HCl Iodine Camphor Naphthalene do not undergo any chemical change when heated, but undergo sublimation Eg: Iodine crystals Iodine vapour 9

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