CHEMISTRY PRACTICAL EXPERIMENT-1 Aim To find the pH of the following samples by using pH paper/universal indicator: a. Dilute Hydrochloric Acid b. Dilute NaOH solution c. Dilute Ethanoic Acid solution d. Lemon juice e. Water f. Dilute Sodium Bicarbonate solution Theory The pH is the measure of the acidic (or basic) power of a solution. It is a scale for measuring hydrogen ion concentration in a solution. The pH scale varies from 0 to 14. At 25°C (298 K), a neutral solution has pH equal to 7. A value less than 7 on the pH scale represents an acidic solution whereas basic solution has pH value more than 7. pH is defined as the negative logarithm (base 10) of the hydrogen ion concentration in moles per litre. pH = -log10[H+] Chemicals Required Dilute HCl, Dilute NaOH Solution, Dilute CH3COOH solution, Fresh Lemon juice, Water and Dilute NaHCO3 solution Apparatus required Test tubes, Test Tubes Stand, Dropper, Glass Rod, pH Paper strips and pH colour chart Procedure Step 1: Six clean test tubes is placed in a test tube stand. Step 2: Dilute HCl, Dilute NaOH Solution, Dilute CH3COOH solution, Lemon juice, Water and Dilute NaHCO3 solution are taken separately in six test tubes and labelled. Step 3: One or two drops of each test solution on different strips of pH papers are put using a glass rod. Glass rod used for one sample must be washed with water before used for the other sample. Step 4: Note the pH by comparing the colour appeared on the pH paper with those on colour chart for pH paper. 5. For determining the pH of lemon juice, squeeze the fruit and place 1 or 2 drop of the juice on the pH paper. Observations Results and Discussions As pH depends upon H+ concentration and in an aqueous solution H+ and OH- ion concentrations are correlated, therefore, every acidic and basic solution shows different colour at different pH. Precautions 1. The test sample solutions should be freshly prepared and the fruit lemon juice samples should also be fresh. 2. Glass rod used for one sample should be used for the other sample only after washing it with water. 3. Acids must be handled carefully. EXPERIMENT-2 Aim To study the properties of HCl by its reaction with: a. Litmus solution (Blue/Red) b. Zinc metal c. Solid sodium carbonate Theory Acids are compounds that contain hydrogen and which dissolve in water to produce hydrogen ions (H +). Ions are particles that have an electrical charge. The hydrogen ions give acids their special properties but they only exist in solution, so an acid only displays its properties when it is dissolved in water. For example, HCI + aq → 4H+ (aq) + Cl- (aq) The more H+ ions are in a solution, the more acidic it will be. • HCl is an acid which turns blue litmus red • HCl reacts with zinc metal to form zinc chloride and hydrogen • HCl reacts with solid sodium carbonate to release CO2 gas Na2CO3 (s) + 2HCl (aq) → 2NaCl + H2O + CO2 Chemicals Required Hydrochloric acid, Litmus solution (Blue and Red), Zinc metal, Sodium carbonate, Sodium hydroxide, Apparatus Required Test tubes, Test tube stand, Bunsen Burner, Matchstick and Dropper Procedure and Observations Table S.No. Procedure 1. Test with Litmus Solution (a) A little amount of blue litmus solutions is taken in a test tube and few drops of HCl is added to it using a dropper. 2. (b) A little amount of red litmus solutions is taken in a test tube and few drops of HCl is added to it using a dropper. 3. Reaction with Zn metal A clean and dry test tube is taken and zinc metal is added to it and placed it on test tube stand. Few drops of HCl is added on Zn pieces with the help of dropper. 4. Reaction with Na2CO3 A small quantity of solid sodium carbonate is taken in a flask and distilled water is added into it. The flask is corked with a double bore cork and a thistle funnel is inserted into the flask. Then a beaker containing lime water near the flask is placed. Then one end of the delivery tube is inserted into the flask and the other end into the beaker. HCl is added into the flask through the thistle funnel and the change in colour of the lime water is observed. Observation (a) Blue litmus turns red. (b) No changes in the colour of red litmus. HCl is an acid having pH value below 7. 2 A gas is evolved which burns with popping sound when a matchstick is brought near the mouth of the test tube. The gas evolved is hydrogen. Zn(s) + HCl(aq) → ZnCl2 + H2 A gas is evolved which turns lime water milky. The gas produced is carbon dioxide which gives brisk effervescence. Na2CO3(s) + 2HCl(aq) → 2NaCl + H2O + CO2 Result 1. Hydrochloric acid turns blue litmus paper to red and shows no effect with red litmus solution. 2. Hydrochloric acid gives hydrogen gas when a piece of zinc is dipped in it. 3. Hydrochloric acid gives carbon dioxide gas with sodium carbonate. Precautions 1. Hydrochloric acid should be handled with care because it can bum skin and clothes. 2. Only small quantity of chemicals should be used. 3. Hands should be cleaned properly after completing the experiments. 4. All the observations should be noted carefully. EXPERIMENT-3 Aim To perform the reaction between sodium sulphate and barium chloride solutions and classify it on: i. Combination reaction ii. Decomposition reaction iii. Displacement reaction iv. Double displacement reaction Theory (a) Barium chloride and Sodium sulphate reacts in an aqueous solution to give precipitate of barium sulphate. Reaction: BaCl2(aq) + Na2SO4(s) → BaSO4(s) + NaCl(aq) (c) Since, there is displacement in both the reactants, it is a case of double displacement reaction. Chemicals Required Sodium sulphate solution, Barium chloride solution, Dilute HCl Apparatus Required Beaker, Test tubes, Glass rod Procedure Step 1: Two test tubes are washed and cleaned. Step 2: About 5 ml of an aqueous solution of barium chloride in one test tube is taken. An equal volume of sodium sulphate solution is taken in another test tube. Step 3: A 50 ml beaker is taken. Step 4: Barium chloride solution is added to the sodium sulphate solution in the beaker. Step 5: The colour of the precipitate so formed is noted. Observation When the solutions of sodium sulphate and barium chloride are mixed a white precipitate is formed which is insoluble in HCl. Inference 1. When sodium sulphate chemically reacts with barium chloride in the form of their aqueous solutions, white precipitate of barium sulphate appears. This confirms the presence of sulphate (SO 4)2- ions. Reaction: BaCl2(aq) + Na2SO4(s) → BaSO4(s) + NaCl(aq) Precautions 1. Handle the acids and alkali carefully. 2. Use equal volumes of barium chloride and sodium sulphate solutions. 3. Clean the apparatus thoroughly before using it.
