CBSE 10th Standard Science Subject Acids, Bases and Salts Chapter Case Study Questions 2021
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CBSE 10th Standard Science Subject Acids, Bases and Salts Case Study Questions 2021
10th Standard CBSE
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Reg.No. :
Science
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Baking powder produces carbon dioxide on heating, so it is used in cooking to make the batter spongy. Although, baking soda also produces CO2 on heating, but it is not used in cooking because on heating, baking soda produces sodium carbonate along with carbon dioxide. Sodium carbonate, thus, produced, makes the taste bitter. Baking powder is the mixture of baking soda and a mild edible acid. Generally, tartaric acid is mixed with baking soda to make baking powder. When baking powder is heated, NaHCO3 decomposes to give CO2 which makes bread and cake fluffy. Tartaric acid helps to remove bitter taste due to formation of sodium tartrate.
\(2 \mathrm{NaHCO}_{3}+ \ \ \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{6} \quad \longrightarrow \quad 2 \mathrm{CO}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{Na}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}\)
Baking soda Tartaric acid Carbon dioxide Sodium tartrate
(i) On passing excess CO2 gas in aqueous solution of sodium carbonate, the substance obtained is(a) NaOH (b) NaHCO3 (c) Na2CO3 ·10H2O (d) Na2CO3 ·H2O (ii) When sodium hydrogen carbonate is added to acetic acid, it evolves a gas. Which of the following statements are true about the gas evolved?
(I) It turns lime water milky
(II) It extinguishes a burning splinter
(III) It dissolves in a solution of sodium hydroxide
(IV) It has a pungent odour(a) (I) and (II) (b) (I), (II) and (III) (c) (II), (III) and (IV) (d) (I) and (IV) (iii) Select the correct statement regarding sodium hydrogen carbonate.
(a) CO and CO2 are produced during the heating ofNaHCO3 (b) It is insoluble in water. (c) It is used in soda-acid fire extinguishers. (d) All of these (iv) Acetic acid was added to a solid X kept in a test tube. A colourless and odourless gas was evolved. The gas was passed through lime water which turned milky. It was concluded that
(a) solid X is sodium hydroxide and the gas evolved is CO2 (b) solid X is sodium bicarbonate and the gas evolved is CO2 (c) solid X is sodium acetate and the gas evolved is CO2 (d) solid X is sodium chloride and the gas evolved is CO2 (v) Which of the following statements are correct regarding baking soda?
(I) Baking soda is sodium hydrogen carbonate
(II) On heating, baking soda gives sodium carbonate
(III) It is used for manufacture of soap
(IV) It is an ingredient of baking powder(a) I and IV only (b) I, II and III only (c) I, II and IV only (d) I, II, III and I (a) -
Bleaching powder is also known as chloride of lime. It is a solid and yellowish white in colour. Bleaching powder can be easily identified by the strong smell of chlorine. When calcium hydroxide (slaked lime) reacts with chlorine, it gives calcium oxychloride (bleaching powder) and water is formed. Aqueous solution of bleaching powder is basic in nature. The material to be bleached is first passed through solution of NaOH to remove greasy matter. Then it is passed through aqueous solution of bleaching powder and very dil. HCI solution. HCI reacts with bleaching powder to liberate nascent oxygen which bleaches material.
(i) Bleaching powder is used as(a) bleaching agent in textile, paper and jute industry (b) disinfectant for water to make water free of germs (c) oxidising agent in many industries (d) all of these (ii) Bleaching powder is also known as
(a) calcium oxychloride (b) calcium hypochlorite (c) chloride of lime (d) all of these. (iii) Bleaching powder gives smell of chlorine because it
(a) is unstable (b) gives chlorine on exposure to atmosphere (c) is a mixture of chlorine and slaked lime (d) contains excess of chlorine (iv) Select the correct statement(s) regarding bleaching powder.
(a) It is pale yellow powder having smell of chlorine (b) It is sparingly soluble in water and gives milky suspension when dissolved in water (c) As bleaching powder gives nascent oxygen, it shows bleaching property (d) All of these (v) Identify the product 'X' in the given reaction \(\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Cl}_{2} \longrightarrow X+\mathrm{H}_{2} \mathrm{O}\)
(a) CaOCl2 (b) CaCl2 (c) Ca(CIO3 )2 (d) CaCO3 (a) -
The preparation of washing soda is carried out through following steps:
Step-I: Manufacture of sodium hydrogen carbonate:\(\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}+\mathrm{NH}_{3}+\mathrm{CO}_{2} \longrightarrow \ \mathrm{NaHCO}_{3}+ \ \mathrm{NH}_{4} \mathrm{Cl}\)
Sodium hydrogen carbonate
Step-II: Thermal decomposition of sodium hydrogen carbonate: When dry crystals of sodium hydrogen carbonate are heated strongly, they decompose to form anhydrous sodium carbonate (soda ash). \(2 \mathrm{NaHCO}_{3(s)} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3(s)}+\mathrm{CO}_{2(g)}+\mathrm{H}_{2} \mathrm{O}_{(g)}\)
Step-III: Recrystallisation of sodium carbonate: Sodium carbonate thus obtained is recrystallised to form crystals of washing soda.\(\mathrm{Na}_{2} \mathrm{CO}_{3(s)}+ 10 \mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}_{(s)}\)
Anhydrous Washing soda
sodium carbonate
(i) Some of the uses of washing soda are given below:
(I) It is used for removing permanent hardness of water
(II) It is used in glass industry
(III) It is used in paper industry
(IV) It is used in the manufacture of sodium compounds such as borax
Select the correct option regarding uses of washing soda(a) (I) and (II) only (b) (II) and (III) only (c) (II) and (IV) only (d) (I), (II), (III) and (IV) (ii) What products will be formed along with water when sodium carbonate reacts with dilute hydrochloric acid?
(a) CO and NaCI (b) Na and CO2 (c) NaCI and CO2 (d) Na and CO (iii) Chief raw materials for the manufacture of washing soda are
(a) sodium chloride, ammonia and limestone (b) ammonia, sodium hydrogen carbonate and copper sulphate (c) sodium hydroxide, calcium chloride and ammonia (d) calcium chloride, sodium chloride and copper sulphate. (iv) What is the action of sodium carbonate on litmus paper?
(a) Turns red litmus blue (b) Turns blue litmus red (c) No change on litmus (d) Both (a) and (b) (v) What products will be obtained when solution of sodium carbonate and slaked lime is heated?
(a) NaOH and CaCl2 (b) CaCO3 and NaOH (c) NaHCO3 and NaOH (d) NaCI and CaCO3 (a) -
"Indicator is a chemical compound which is added to the solution in very small amount to detect its acidic or basic nature:" As they show colour change in acidic and basic medium, they are also called acid-base indicators. In other words, "an acid-base indicator is that substance which possesses one colour in acidic medium and a different colour in alkaline medium:''
Indicators, basically, are coloured organic substances either extracted from plants (natural indicators) or synthesised in the laboratory (synthetic indicators). A few common acid base indicators are: Litmus, phenolphthalein, methyl orange etc. In addition to these there are some naturally occurring substances which have different smell in acidic and basic medium. These substances are called olfactory indicators.
(i) Which one of the following will turn red litmus blue?(a) Vinegar (b) Baking soda solution (c) Lemon juice (d) Soft drinks (ii) A solution turns blue litmus red. The pH of the solution is probably
(a) 8 (b) 10 (c) 12 (d) 6 (iii) A solution in test tube 'A' turns red litmus blue, evolves hydrogen gas on reaction with zinc and does not react with sodium carbonate. Whereas, solution in test tube 'B' turns blue litmus red, liberates hydrogen gas on reaction with zinc and evolves carbon dioxide gas with sodium carbonate. Identify 'A' and 'B'
(a) 'A' is an acid, 'B' is a base (b) 'A' is a base, 'B' is an acid (c) Both 'A' and 'B' are bases (d) Both 'A' and 'B' are acids (iv) Select the incorrect option
Indicator Colour in acidic medium Colour in basic medium (a) Litmus (Purple) Red Blue (b) Flower of hydrangea plant (Blue) Red Green (c) Red cabbage juice (Purple) Red or Pink Green (d) Turmeric Juice (Yellow) Yellow Reddish brown (v) Which one of the following can be used as an acid-base indicator by visually impaired student?
(a) Litmus (b) Turmeric (c) Vanilla essence (d) Methyl orange (a) -
Acids turn blue litmus red but have no effect on red litmus. Bases turn red litmus blue but have no effect on blue litmus. The sample in which phenolphthalein remains colourless while methyl orange changes to pink/ red are acids while the samples in which phenolphthalein colour changes to pink and methyl orange changes to yellow are bases. Some observations of different sample solutions in litmus, phenolphthalein and methyl orange indicator are given in the table.
Sample solution Red litmus solution Blue litmus solution Phenolphthalein indicator Methyl orange indicator
HCI No colour change Red Colourless Red/ Pink H2 SO4 No colour change Red Colourless Red/ Pink HNO3 No colour change Red Colourless Red/ Pink CH3COOH No colour change Red Colourless Red/ Pink NaOH Blue No colour change Pink Yellow Ca(OH)2 Blue No colour change Pink Yellow KOH Blue No colour change Pink Yellow Mg(OH)2 Blue No colour change Pink Yellow NH4 OH Blue No colour change Pink (Becomes colourless after sometime) Yellow (Becomes colourless after sometime) (i) Which of the following substances does not turn red litmus solution to blue?
(a) AI(OH)3 (b) Mg(OH)2 (c) H3 PO4 (d) NH4OH (ii) Phenolphthalein's colour in basic medium is ___________but in acid it is ___________ .
(a) pink, colourless (b) yellow, pink (c) pink, orange (d) blue, red (iii) Which of the following acids are edible?
(I) Citric acid
(II) Tartaric acid
(III) Hydrochloric acid
(IV) Carbonic acid.(a) (I) and (II) only (b) (1), (II) and (IV) only (c) (I), (II) and (III) only (d) (I), (II), (III) and (IV) (iv) The colour of methyl orange in neutral solution is
(a) red (b) orange (c) yellow (d) purple (v) Which of the following cannot act as an indicator?
(a) Methyl orange (b) Methyl chloride (c) Turmeric juice (d) Phenolphthalein (a)
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CBSE 10th Standard Science Subject Acids, Bases and Salts Case Study Questions 2021 Answer Keys
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\({ (i) }(\mathrm{b}): \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} \longrightarrow 2 \mathrm{NaHCO}_{3}\)
(ii) (b): \(\mathrm{NaHCO}_{3}+\mathrm{CH}_{3} \mathrm{COOH} \longrightarrow \mathrm{CH}_{3} \mathrm{COONa}\) \(+\mathrm{CO}_{2} \uparrow+\mathrm{H}_{2} \mathrm{O}\)
Carbon dioxide gas is evolved which turns limewater milky. It extinguishes a burning splinter since it is not a supporter of combustion. It dissolves in sodium hydroxide solution and it is an odourless gas.
\({ (iii) }(\mathrm{c}): 2 \mathrm{NaHCO}_{3} \stackrel{\text { Heat }}{\longrightarrow} \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}\)
NaHCO3 is soluble in water.
\({ (iv) }(\mathbf{b}): \mathrm{NaHCO}_{3}+\mathrm{CH}_{3} \mathrm{COOH} \longrightarrow\) \(\mathrm{CH}_{3} \mathrm{COONa}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}\)
(v) (c): It is not used in manufacture of soap. -
(i) (d)
(ii) (d)
(iii) (b): Bleaching powder gives chlorine on exposure to air by reacting with CO2 . \(\mathrm{CaOCl}_{2}+\mathrm{CO}_{2} \longrightarrow \mathrm{CaCO}_{3}+\mathrm{Cl}_{2}\)
(iv) (d)
\({ (v) }(\mathrm{a}): \mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Cl}_{2} \longrightarrow \mathrm{CaOCl}_{2}+\mathrm{H}_{2} \mathrm{O}\) -
(i) (d)
(ii) (c): Na2CO3 reacts with dilute acids to give COgas with brisk effervescence.
\(\mathrm{Na}_{2} \mathrm{CO}_{3(s)}+2 \mathrm{HCl}_{(a q)} \longrightarrow 2 \mathrm{NaCl}_{(a q)}+\mathrm{H}_{2} \mathrm{O}_{(l)}\)\(+\mathrm{CO}_{2(g)} \uparrow\)
Sodium Dil. Hydrochloric Sodium Water Carbon dioxide
carbonate acid chloride
(iii) (a): Chief raw materials for the manufacture of washing soda are sodium chloride (NaCl), ammonia (NH3 ) and limestone (CaCO3)
(iv) (a): Sodium carbonate turns red litmus blue
(v) (b): Sodium hydroxide and calcium carbonate are formed when the solution of sodium carbonate and slaked lime, Ca(OH)2 is heated \(\mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{Ca}(\mathrm{OH})_{2} \longrightarrow 2 \mathrm{NaOH}+\mathrm{CaCO}_{3}\) -
(i) (b): Baking soda (NaHCO3) is basic in nature.
(ii) (d): The solution turns blue litmus red, hence it is acidic.
(iii) (b): Acids turn blue litmus red, liberate hydrogen gas with zinc and evolve carbon dioxide gas with metal carbonates. Bases turn red litmus blue, evolve hydrogen gas with zinc and do not react with metal carbonates
(iv) (b):Indicator Colour in acidic Colour in basic medium Flowers of hydrangea plant (blue) Blue Blue (v) (c): Vanilla essence is an olfactory indicator. So, its smell is different in acidic and basic medium which can be detected easily by a visually impaired student.
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(i) (c)
(ii) (a)
(iii) (b): Citric and tartaric acid are from organic substances such as lemon and tamarind respectively and they are edible. Hydrochloric acid though formed inside stomach is not edible. Carbonic acid is a mild acid and is edible in the form of soda water.
(iv) (b)
(v) (b)
