Question 1.With the help of an example explain what happens when a base reacts with a non- metallic oxide. What do you infer about the nature of non-metal oxide? (Board Term I, 2017)Answer:Oxides of non-metals react with bases to form salt and water. For example, the reaction between carbon dioxide and calcium hydroxide. Calcium hydroxide, which is a base, reacts with carbon dioxide to produce salt and water.Hence, oxides of non-metals are acidic in nature.
Question 3.2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the content are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid.Answer:It is observed that active metals like zinc react with strong bases like NaOH, KOH etc. to liberate hydrogen gas and corresponding salt.
acid bases and salts class 10 icse pdf 27
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Question 12: How many types of salts can be prepared from orthophosphoric acid ? Is there any difference in the salts formed by the acid ? Answer: There are three types of salts prepared from orthophosphoric acid [H3PO4], two acidic salts and one normal salt. These salts are obtained by the stepwise replacement of hydrogen atom from orthophosphoric acid. For example: The acidic salts obtained from orthophosphoric acid have the capacity to ionize further to yield hydrogen ion and thus they can change blue litmus paper red, whereas normal salt does not.
Question 17: Name, from the list of substances given below, the substance which you would use to prepare each of the following salts named in Part (i) to (iv). The substances are: Dilute sulphuric acid, copper, lead, dilute nitric acid, dilute hydrochloric acid, copper oxide, lead carbonate, sodium carbonate, sodium and zinc. (i) Lead sulphate. (ii) Copper sulphate. (iii) Sodium sulphate. (iv) Zinc sulphate. (v) What are the two steps necessary to change lead carbonate into lead chloride ? (vi) Give the name of a soluble lead salt and write the equation for the action of heat on this salt. Answer: (i) For lead sulphate lead carbonate and dilute sulphuric acid are required. (ii) For copper sulphate copper oxide and dilute sulphuric acid are required. (iii) For sodium sulphate sodium carbonate and dilute sulphuric acid are required. (iv) For zinc sulphate zinc and dilute sulphuric acid are required.
Question 18: Name the method used for preparation of the following salts from the list given below : (i) Sodium nitrate (ii) Iron (III) chloride (iii) Lead chloride (iv) Zinc sulphate (v) Sodium hydrogen sulphate List: (a) Simple displacement (b) Neutralization (c) Decomposition by acid (d) Double decomposition (e) Direct synthesis. Answer: (i) (B) Neutralisation (ii) (E) Direct synthesis (iii) (D) Double decomposition (iv) (A) Simple displacement (v) (C) Decomposition by acid.
Question 2: Some methods used for the laboratory preparation of salts are : A : metal + acid B : carbonate + acid C : precipitation (double decomposition) D : direct combination E: titration Copy and complete the following table:
Question 4: Garbonic acid is a dibasic acid. Why ? Answer: Carbonic acid (H2CO3) is a dibasic acid because it has two replaceable hydrogen atoms and hence it combines with two hydroxyl groups of the bases to form two kinds of salt and water. The displacement of two hydrogen atoms takes place in two steps.
Question 9: An aqueous solution of sodium carbonate is alkaline and that of ammonium chloride is acidic in behaviour. Why? Answer: Both of these salts react with water. Sodium carbonate reacts with water, producing a strong alkali, sodium hydroxide and a weak acid, carbonic acid. Hence, the solution is alkaline: Ammonium chloride reacts with water to produce ammonium hydroxide, a weak alkali and hydrochloric acid, a strong acid. Hence the solution is acidic:
Question 11: The heat of neutralization of a strong acid with strong base is always the same. Why? Answer: Strong acids, strong bases and their salts ionize completely in the solution. Consider the neutralization of hydrochloric acid by sodium hydroxide, which is as follows: This shows that heat of neutralization of a strong acid by a strong base is nothing, but heat of formation of water molecule from hydrogen and hydroxyl ions, hence it is in the same and fixed quantity.
Question 16: Sodium sulphite (Na2SO3) and sodium hydrogen sulphite (NaHSO3) are salts of sodium but sodium sulphite is called a normal salt and sodium hydrogen sulphite is called an acid salt. Why? Answer: Sodium hydrogen sulphite has replaceable hydrogen in its molecule so it is called an acid salt but sodium sulphite does not have, so it is called a normal salt.
Question 4.List two differences between acids and bases on the basis of chemical properties.Answer:(i) Dilute acids like HCl and H2SO4 evolve H2 gas on reacting with metals like Zn, Mg and Ca, etc. and dilute bases do not evolve hydrogen gas.(ii) Acids react with oxides of metals while bases react with oxides of non-metals.
Question 8.Classify the solutions of the following as acids, bases and salts:Ammonium hydroxide, barium chloride, sodium chloride, sodium hydroxide, sulphuric acid and nitric acid.Answer:
Question 4.Manshi is a student of class X in a city school. There was a tall tree at the edge of the garden having a large honeycomb attached to it. Some students were playing cricket in the school playground. Suddenly the cricket ball hit the honeycomb due to which a large number of honey-bees started flying here and there. Manshi was stung on her face by a honey-bee. The sting was so painful that Manshi started crying. One of her classmates Shanti quickly got some baking soda and made a paste of it with water. Then she applied the paste on the stung area of the face. On rubbing baking soda solution, Manshi felt a lot of relief from the pain.(a) What kind of liquid is injected into the skin when honey-bee strings?(b) Why did rubbing baking soda solution on the stung area of skin give relief from pain?(c) What type of chemical reaction takes place when baking soda solution is rubbed on the area stung by honey-bee?(d) What values are exhibited by Shanti and the classmates?Answer:(а) Honey-bee sting injects an acidic liquid into the skin.
(30) Ans:- This is because antacids are a group of mild bases which have no toxic effects on the body . For Basic in nature antacids react with excess acid in the stomach and neutralize it. This give us relief.
Q.19. Assertion : Antacids neutralize the effect of extra acid produced in the stomach during indigestion and thus provide relief.Reason: Antacids are mild bases. 2ff7e9595c
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