CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar 5 Mark Questions 2021
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CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar 5 Mark Questions 2021
10th Standard CBSE
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Reg.No. :
Science
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In the following schematic diagram for the preparation of hydrogen gas as shown in Figure, what would happen if following changes are made?
(a) In place of zinc granules, same amount of zinc dust is taken in the test tube.
(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.
(c) In place of zinc, copper turnings are taken.
(d) Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.(a) -
For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,
(a) How will it affect the taste of the cake and why?
(b) How can baking soda be converted into baking powder?
(c) What is the role of tartaric acid added to baking soda?
(a) -
A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y; it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.
(a) -
A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by-product of chlor-alkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
(a) -
A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance. Which can be moulded into different shapes by making its dough. When this compound is left in open for sometime, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.
(a)
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CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar 5 Mark Questions 2021 Answer Keys
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(A) Hydrogen gas will evolve with greater speed.
(B) Almost same amount of gas is evolved.
(C) Hydrogen gas is not evolved.
(D) If sodium hydroxide is taken, hydrogen gas will be evolved.\(Zn+2NaOH\rightarrow \underset{Sodium\ zincate}{Na_2ZnO_2}+H_2\) -
(a) Baking soda is sodium hydrogen carbonate. On heating, it is converted carbonate. On heating, it is converted into sodium carbonate which is bitter to taste.
\(2NaHCO_3\xrightarrow{Heat}Na_2CO_3+H_2O+CO_2\)
(b) Baking soda can be converted into baking powder by the addition of appropriate acid to it.
(c) The role of tartaric acid is to neutralise sodium carbonate and cake will not taste bitter.
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The gas evolved at anode during electrolysis of brine is chlorine (G) When chlorine gas is passed through dry \(Ca(OH)_2\ (Y)\) produces bleaching powder (Z) used for disinfecting drinking water.
\(Ca(OH)_2+Cl_2\rightarrow CaOCl_2+H_2O\)
Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.
\(CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\)
\(Ca(OH)_2+CO_2 \rightarrow CaCO_3+H_2O\) -
Sodium hydroxide (NaOH) is a commonly used base and is hygroscopic, that is, it absorbs moisture from the atmosphere and becomes sticky. The acidic oxides react with base to give salt and water. The reaction between NaOH and \(CO_2\) can be given as \(2NaOH+CO_2\rightarrow Na_2CO_3+H_2O\)
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The Substance which is used for making different shapes is Plaster of Paris. Its chemical name is calcium sulphate hemihydrate \([CaSO_4.1/2H_2O].\) The two formula unit of \(CaSO_4\) share one molecule of water. As a result, it is soft. When it is left open for some time, it absorbs moisture from the atmosphere and forms gypsum, which is a hard solid mass.
\(\underset{Plaster\ of\ Paris}{CaSO_4.{1\over 2}H_2O}+1{1\over2}{H_2O}\rightarrow \underset{Gypsum}{CaSO_4.2H_2O}\)
