Re: Acid Bases And Salts Class 10 Icse Pdf 27
Vinnie Breidenthal
Selina Publishers for class 10 Chemistry chapter 3 talks about the definition and properties of acids and bases. The chapter further deals with different reactions and students mainly learn how acids and bases react in different circumstances. They are also taught about real-world acids and their uses. Hence, students who want to get familiar with all the topics, equations and understand them clearly can access free concise Chemistry class 10 ICSE solutions for chapter 3 given here. The solutions can be downloaded easily and are available in the form of a PDF. Students can use them at their convenience to learn all the answers to difficult questions, understand and practice reactions and in the process be well prepared to write the exams.
5. You have been provided with three test tubes. One of them contains distilled water and the other two have an acidic solution and a basic solution respectively. If you are given red litmus paper, how will you identify the contents of each test tube?
By the concept of neutralization, we know that acidic and basic solutions neutralize each other. Thus, we can distinguish between the three types of solutions and identify the contents of each test tube.
Pink12. What do you understand by pH value? Two solutions X and Y have pH values of 4 and 10, respectively. Which one of these two will give a pink colour with a phenolphthalein indicator?
An acid-base indicator like litmus gives information only whether a given substance is an acid or a base. The universal indicator gives a complete picture to how acidic or basic a substance is by giving different colours for solutions of different pH values.
Items like chocolates and sweets are degraded by bacteria present in our mouth. Tooth decay starts in humans start when the pH falls below 5.5. So, due to the lower pH values, the tooth enamel which is the hardest substance in our body gets corroded. The saliva produced by salivary glands is slightly alkaline and this helps to increase the pH to some extent. But in order to prevent this one can brush their teeth with toothpaste as it contains a basic substance which is used to neutralize excess acid in the mouth.
17. When you use universal indicator, you see that solutions of different acids produce different colours. Indeed, the solution of the same acid with different concentrations will also give different colours. Why?
The more acidic solutions turn universal indicator bright red. A less acidic solution will only turn it orange-yellow. Colour differences can be noticed in case of vinegar which is less acidic and battery acid which is more acidic.
Take dilute sulphuric acid in a beaker and heat it on wire gauze. Add cupric oxide in small quantities at a time, with stirring till no more of it dissolves and the excess compound settles to the bottom.
Filter it hot and collect the filtrate in a china dish. Evaporate the filtrate by heating to the point of crystallization and then allow it to cool and collect the crystals of copper sulphate pentahydrate.
Take dilute sulphuric acid in a beaker and heat it on wire gauze. Add some granulated zinc pieces with constant stirring. Add till the Zinc settles at the base of the beaker. Effervescences take place because of the liberation of hydrogen gas. When effervescence stops, it indicates that all the acid has been used up. The excess of zinc is filtered off. Collect the solution in a china dish and evaporate the solution to get crystals. Filter, wash them with water and dry them between the folds of paper. The white needle crystals are of hydrated Zinc sulphate.
Metallic lead is converted to lead oxide by oxidation. Then lead sulphate is prepared from insoluble lead oxide, by first converting it into soluble lead nitrate. Then the lead nitrate solution is treated with sulphuric acid to obtain white ppt. of Lead sulphate.
Dissolve 5 grams of anhydrous sodium carbonate in about 25 ml of distilled water in a flask. Cool the solution by keeping the flask in a freezing mixture. Pass carbon dioxide gas in the solution. Crystals of sodium bicarbonate will precipitate out after some time. Filter the crystals and dry it in folds of filter paper.
An acid is a compound which when dissolved in water forms hydronium ions as the only positively charged ions. A base is a compound which is soluble in water and contains hydroxide ions. A base reacts with an acid to form a salt and water only. This type of reaction is known as neutralisation.
(a) As sodium hydroxide and sulphuric acid are both soluble, an excess of either of them cannot be removed by filtration. Hence, it is necessary to find out the ratio of reactants required in the preparation of sodium sulphate.
19. Which of the following methods, A, B, C, D or E is generally used for preparing the chlorides listed below from (i) to (v). Answer by writing down the chloride and the letter pertaining to the corresponding method. Each letter is to be used only once.
2. M is an element in the form of a powder. M burns in oxygen and the product obtained is soluble in water. The solution is tested with litmus. Write down only the word which will correctly complete each of the following sentences.
(a) Efflorescence is the property of some salts to lose wholly, or partly their water of crystallisation when their crystals are exposed to dry air even for a short time. Such substances are called efflorescent substances.
(b) Certain water-soluble salts which on exposure to the atmosphere at ordinary temperature, absorb moisture from the atmospheric air and dissolve in the absorbed water, forming a saturated solution. This phenomenon is called deliquescence and the salts are called deliquescent.
(a) Sodium hydrogen sulphate [NaHSO4] is an acid salt and is formed by the partial replacement of the replaceable hydrogen ion in a dibasic acid [H2SO4]. The [H] atom in NaHSO4 makes it behave like an acid.
(a) Table salt turns moist as it absorbs the water and water vapour present in the air, especially during the rainy season as it has high humidity. Pure sodium chloride is not deliquescent, but the commercial version of the common salt has impurities such as magnesium chloride and calcium chloride which are deliquescent substances.
(b) By passing a current of dry hydrogen chloride gas through a saturated solution of the affected salt the impurity can be removed. As a precipitate pure sodium chloride is produced which can be recovered by filtering and washing first with some water and finally with alcohol.
Water is not added to acid as it is an exothermic process and in this process so much heat is produced that splashing of acidic acid solution may occur, also the container may break which can be fatal to the person.
(a) Carbonic acid is a dibasic acid i.e., it has two replaceable hydrogen ions. Hence, it forms one acid salt or one normal salt. On the other hand, hydrochloric acid is a monobasic acid with one replaceable hydrogen ion. Hence, it forms only one normal salt.
(b) Concentration of an acid means the amount of water present in the acid and not at all the strength of an acid. Strength of an acid is the measure of concentration of hydronium ions it produces in its aqueous solution. Thus, dil. HCl is stronger acid than highly concentrated acetic acid.
(c) H3PO3 is not a tribasic acid but dibasic because in oxyacids of phosphorus, hydrogen atoms which are attached to oxygen atoms are replaceable. Hydrogen atoms directly bonded to phosphorus atoms are not replaceable.
(d) Generally, acids liberate carbon dioxide on reaction with metallic carbonates and bicarbonates. But if the salt produced is insoluble, then the reaction does not proceed. So, we do not expect lead carbonate to react with hydrochloric acid.
You have been provided with three test tubes. One of them contains distilled water and the other two have an acidic solution and a basic solution respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
(a) The colour of litmus paper changes only in presence of ions like hydrogen [H+] or hydronium ions [H3O+]. HCl can produce these ions only in the form of aqueous solution. Hence, dry HCl gas does not change the colour of dry litmus paper.
(b) A base reacts with an acid to form salt and water ONLY. The word ONLY is of importance in the definition of a base. Lead oxide reacts with hydrochloric acid to produce lead (II) chloride (a salt) and water, but the word "only" excludes it from the class of bases because chlorine is also produced.
Alkalis react with oil to form soap. Since, our skin contains oil hence when we touch strong alkalis, a reaction takes place and soapy solutions are formed. This reaction can be corrosive for skin. Hence we should wear gloves while working with strong alkalis.
Substances like chocolates and sweets are degraded by bacteria present in our mouth. When the pH falls to 5.5 tooth decay starts. Tooth enamel is the hardest substance in our body and it gets corroded. The saliva produced by salivary glands is slightly alkaline, it helps to increase the pH, to some extent, but toothpaste which contains basic substance is used to neutralize excess acid in the mouth.
When you use a universal indicator, you see that solutions of different acids produce different colours. Indeed, solutions of the same acid with different concentrations will also give different colours. Why?
Universal indicators give different colours at different concentrations of hydrogen ions in a solution. The hydrogen ion concentration differs for the same acid with different concentrations. Hence, the universal indicator gives different colours for the same acid with different concentrations.
(a) A solution with pH of 7 is neutral. (i) Increasing it's pH means increasing its basic nature. Hence, we will add alkali to increase it's pH. (ii) Similarly, to decrease it's pH, we will add an acid to the solution.
M is an element in the form of powder. M burns in oxygen and the product obtained is soluble in water. The solution is tested with litmus. Write down only the word which will correctly complete each of the following sentences.
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