14 øŒ‰vÚÛî¦ô¢Ù 13 è…šúÙñô¢ª 2019 email: [email protected] (X + Y) solution with inversal indicator. A: H 'X' is an acid H 'Y' is a base Water of Crystallization means? H (X + Y) is neutral solution. H Hence (X + Y) solution changes into green with universal solution. Acids, Bases and Salts 3) Washing Soda 4) Bleaching powder 8. What will happen if we test dry HCl with dry 4. Match the important chemicals given in column blue litmus paper? Why? Two Marks Questions A with the chemical formula given in colum B A: H Colour of blue litmus paper does not change. Column A Column B H Dry HCl do not release H+ ions. Hence is 1. What is a neutralization reactoin? Give one a) Plaster of paris i) Ca(OH) not behave as an acid. example. 2 1 9. A white powder 'A' is a mild non - corrosive b) Gypsum ii) CaSO4 ⎯ H2O A: Neutralization reaction: The reaction 2 base and is used in the preparation of between an acid and a base to give salt and c) Bleaching powder iii) CaSO4 2H2O cakes. When the powder is heated, it gives water is known as a neutralization reaction d) Quick lime iv) CaOCl2 another powder 'B'. The powder 'B' is Acid + Base → Salt + Water A: a-ii b-iii c-iv d-i recrystallized to get a substance 'C' which e.g.: HCl + NaOH → NaCl + H2O has detergent properties. Identify A, B and (aq) (aq) (aq) 5. Substance A changes the blue litmus paper into red colour. Substance B changes the C and also write balanced chemical equa- red litmus paper into blue colour. Now tions for the conversions of A and B. Writer answer the following questions. A: A → Baking soda (NaHCO3) D.V. Subba Naidu i) What is the name of reaction that takes Target-2020 B → Sodium carbonate (Na2CO3) Subject Expert place between A and B? C → Washing soda (Na2CO3H2O) ii) What are the compounds formed, if A Tenth Chemical equation 2. If a few drops of a concentrated acid acci- and B react with each other. 100 2 NaHCO3 → Na2CO3 + H2O + CO2 dentally spills over the sand of a student, A: i) A - Acid B - Base 100 Physical Science 10. Which product will form when CaO is dis- what should be done? The reaction between A and B is called solved in water? How do you find the A: Wash the hand immediately with plenty of neutralization reaction A: i) When Zinc reacts with HCl as well as nature of product? water and apply a paste of sodium hydro- ii) Salt and water are formed when A and B NaOH, Hydrogen gas is produced. A: When CaO (Quick lime), Calcium oxide is gen carbonate. react with each other. ii) Hydrogen gas puts off the flame with dissolved in water (H2O), Calcium hydrox- ide (Ca(OH) ) solution is formed. 3. Name the four chemicals that are obtained 6. What is the common observation made by 'pop' sound. 2 from common salt? you example while conducting the experi- 7. Solution 'X' turned blue litmus paper into CaO + H2O → Ca(OH)2 A: 1) Sodium hydroxide ment with Zinc and both HCl and NaOH red. Solution 'Y' turned phenolphthalein When red litmus paper is dipped in the solution, 2) Baking soda separately? How can you find it? solution into pink. Predict the result of test it turn blue. So, the solution is basic nature. Also give the common method to get relief solutions. e.g.: Vanilla essence 1 One Mark Questions ⎯ Mark Questions from the discomfort caused by the honey- 7. Which bases are called alkalies? Give an 2 bee sting. 1. What is the pH scale? example of alkali? 1. A Solution reacts with crushed egg-shells A: pH Scale: pH is defined as the negative A: Methanoic acid is present in bee sting. A: Water soluble bases are called alkalies. to give a gas that turns lime - water milky. logarithm of hydrogen ions [H+] concentra- When baking soda is rubbed on the affect- Examples of alkalies are NaOH, KOH etc. What is the nature of solutions? + ed part, it gives relief from pain. tion. pH = −log10 [H ]. 8. To prevent tooth decay we are advised to A: Acidic nature 5. If we keep a clean cloth along with finely brush our teeth regularly. The nature of the 2. Why does the soil of agricultural lands get 2. What is the colour of phenolphthalein tested for pH? chapped onion in plastic bag for few hours. tooth paste commonly used it? Now can we use this cloth as indicator? If indicator in alkaline medium? A: Plants required a specific pH range for A: Basic nature. Basic tooth paste neutralizes yes name the indicator? A: Pink colour their healthy growth. any acid which may be present on teeth. Acid A: We can use this cloth as indicator. This comes because of bacterial activity in mouth. 3. Write the colour of Methyl orange in 3. Write the molecular formula of common type of indicators are called 'olfactory indi- acidic solution. salt and baking soda which are widely used 9. Which substance is used in making toys, cators'. A: Red colour at home? materials for decoration and for making 6. What are olfactory indicators? surface smoth. Write its Chemical formula. A: Common salt - NaCl, Baking soda - 4. The pH values of fine different solutions A: Olfactory indicators are substance which A: Plaster of paris. Chemical formula is A, B, C, D and E are given as 1, 5, 7, 11 NaHCO3 have different odour in acidic and basic 1 and 13 respectively. Which is the 4. Name the acid present in honeybee sting. CuSO4 ⎯2 H2O. strongest acidic solution. A: Solution A Four Marks Questions 2. What is meant by 'water of crystallization' H Now cool the test tube and add 2 - 3 5. Write the formula for 'gypsum'? of substance? Describe an activity to show drops of water to the sample of anhy- A: CaSO . 2H O 1. With the help of pH scale answer the 4 2 the water of crystallization. drous copper sulphate. H We observe 6. With which salt, chlorine reacts to give following questions. A: Water of crystallization: The water of crys- the blue colour of copper sulphate bleaching powder as a product? tallisation is the fixed number of water mol- crystals is restored. H From this pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A: Ca(OH)2 ecules present in one formula unit of salt. activity, we conclude that somewater Sub- 7. What is the range of pH scale? stance P Q R S e.g.: CuSO . 5H O molecules are fixed in the blue coloured 4 2 A: 0 to 14 Acitivity: copper sulphate crystals. i) The pH value of Q is 6. So it is a weak 8. During indigestion, stomach produces H Take a few crystals of copper sulphate in 3. Draw a neat diagram showing a acid acid. Write the natures of solutions 'P' which acid excessively? a dry test tube. H Heat the dry crystals solution in water conducts electricity. Why and 'S'. A: HCl. strongly over the flame of a burner for the solution of sugar and glucose in water ii) Arrange the following solution from 9. When electricity is passed through a some time. H The water present in the do not conduct electricity? concentrated acid to concentrated aqueous solution of sodium chloride, it crystals are evaporated and the blue A: Acid solution have ions and movement of base. Milk, Hydrochloric acid, Sodium decompes to form sodium hydroxide. colour of salt turns to white. H We also these ions helps flow of current but glu- hydroxide, Baking Soda. What do you call this process? see tiny water droplets on the walls of cose and sugar solution do not have free ions iii) If we add the substances 'P' and 'S' in the test tube. and so current does not pass through them. A: Chloro - alkali process. equal quantities what is its nature? 10. Write the name of acid present in vinegar? CuSO4. 5H2O → CuSO4 + 5 H2O AC plug iv) Write the substance gives red colour Bulb Blue colour White colour 230 volt A: Acetic acid with methyl orange indicator. 11. Which colour do you observe, If a few A: i) P - strong acid, S - strong base. drops of NaOH sprinkled on pH paper? ii) Hydrochloric acid, milk, baking soda, Test tube holder Boiling tube A: Violet colour Sodium hydroxide. Water droplets Beaker Copper sulphate crystals 12. Arrange the following in the incresing iii) If 'P' and 'S' added to each other the Burner order of their pH values. solution formed is in neutral and its pH i) Weak acid ii) Weak base value is 7. dil. HCl solution iv) 'P' and 'Q' give red colour with methyl Graphite rods iii) Strong acid iv) Strong base orange indicator. Removing water of crystallisation Acid solution in water conducts electricity A: iii, i, ii, iv.