Question Set A

CBSE 10th Science Acids, Bases and Salts Sample Question Papers Study Material - QB365

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Questions:

Generic 2

5 x 2 = 10

How would you distinguish between baking powder and washing soda by heating?

A compound 'x' on losing partial crystallisation of water gives compound 'y' crystallisation of water gives compound 'y' which is used for making chalk and other pottery articles. But when 'x' is strongly heated, it given 'z' which is used as drying agent, Identify x, y, z and write chemical equations.

We know that metals conduct electricity, also ionic compounds in molten form or in aqueous solution conduct electricity. Is the conduction process in the two cases similar? Explain.

How is the concentration of hydronium ions H₃O⁺affected when a solution of an acid is diluted?

Why should curd and sour substances not be kept in brass and copper vessels?

Generic 3

3 x 3 = 9

(i) Write the name given to bases that are highly soluble in water. Give an example.
(ii) How is tooth decay related to pH? How can it be prevented?
(iii) Why does bee-sting cause pain and irritation? Rubbing of baking soda on the sting area gives relief. How?

(i) Name the raw materials used in the manufacture of sodium carbonate by Solvay process.

(ii) How is the sodium hydrogen carbonate formed during Solvay process separated from a mixture of \(NH_4Cl\) and \(NaHCO_3\)?

(iii) How is sodium carbonate obtained from sodium hydrogen carbonate?

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Multiple Choice Question

5 x 1 = 5

Sodium carbonate is a basic salt because it is a salt of

(a)

Strong acid and strong base

(b)

weak acid and weak base

(c)

strong acid and weak base

(d)

weak acid and strong base

10.

During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to

(a)

absorb the evolved gas

(b)

moisten the gas

(c)

absorb moisture from the gas

(d)

absorb Cl^-ions from the evolved gas

11.

What happens when a solution of an acid is mixed with a solution of a base in a test tube?

(a) The temperature of the solution increases

(b) The temperature of the solution decreases

(d) Salt formation takes place

(a)

(i) only

(b)

(i) and (iii)

(c)

(ii) and (iii)

(d)

(i) and (iv)

12.

10 ml of a solution of NaOH is found to be completely neutralised by 8 ml of a given solution of HCl. If we take 20 ml of the same solution of NaOH, the amount of HCl solution required to neutralise it will be

(a)

4 ml

(b)

8 ml

(c)

12 ml

(d)

16 ml

13.

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains.

(a)

NaCl

(b)

HCl

(c)

LiCl

(d)

KCl

Generic 5

1 x 5 = 5

14.

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.

Passage Based Questions

1 x 1 = 1

15.

The electrolysis is a process in which the solution or molten liquid allows electricity to pass through it. The electrolysis of acid and water conducts electricity and the bulb glows as the circuit is complete.
Answer the following questions based on the above information
(a) Infer the result if alcohol is used instead of acid.
(b) If the acid is replaced by glucose will the bulb glow? Explain
(c) Name the ions produced during the electrolysis of HCl.
(d) What will happen if you replace the above solution in the beaker with molten sodium chloride?

Data Based Questions

1 x 1 = 1

16.

S.No	Salt	Base	Acid	pH
1.	Na₂SO₄	NaOH	H₂SO₄	=7
2.	NH₄Cl	NH₄OH	HCl	<7
3.	KNO₃	KOH	HNO₃	=7
4.	NaCl	NaOH	HCl	=7

Answer the following questions based on the above information
(a) Why is the pH of NH₄Cl less than 7?
(b) What is the nature of ammonium sulphate solution?
(c) NaHCO₃gives brisk-effervescence when reacts with
(i) HCl (ii) NH₄OH (iii) NaOH (iv) K₂CO₃
(d) Which species formed on heating NaHCO₃is used to make bread and cakes fluffy, soft and spongy?
(i) Na₂CO₃ (ii) CO₂ (iii) H₂O (iv) H₂CO₃

Assertion and reason

1 x 1 = 1

17.

Assertion: Aqua regia, is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid
Reason: The two acids (hydrochloric acid and concentrated nitric acid are mixed in the ratio of 3: 1 respectively)
Codes
(a) If both assertion and reason are true and the reason is correct explanation of assertion.
(b) If both assertion and reason are true but reason is not a correct explanation of assertion.
(c) If assertion is true and reason is false.
(d) If both assertion and reason are false

Case Study Questions

2 x 4 = 8

18.

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

19.

Chemically, Plaster of Paris (POP) is calcium sulphate hemihydrate, i.e., containing half molecule of water of crystallisation. It is represented by the formula, CaSO_{4 ·}1/2H₂O. Half molecule of water of crystallisation means that one water molecule is shared by two formula units of CaSO_4. Hence, we also represent its formula as (CaSO₄)_2·H₂O. The name, plaster of Paris, was given to this compound because for the first time, it was made from gypsum which was mainly found in Paris.
(i) The difference of water molecules in gypsum and plaster of Paris is

(a) 5/2

(b) 2

(c) 1/2

(d) 3/2

(ii) Plaster of Paris hardens by

(a) giving off CO₂	(b) changing into CaCO₃
(c) combining with water	(d) giving out water

(iii) Which of the following statements is incorrect?

(a) Plaster of Paris is used to ornate designs on walls and ceilings

(b) On heating gypsum above 373 K, CaSO₄ is obtained

(c) Dead burnt plaster is CaSO₄·2H₂O

(d) Setting of plaster is due to its hydration into gypsum

(iv) Select the incorrect statement with respect to gypsum

(a) It is slightly soluble in water

(b) It is also known as alabaster

(c) On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate

(d) Chemical formula of gypsum is CaSO₄ ·1/2H₂O

(v) Plaster of Paris is obtained by

(a) adding water to calcium sulphate.

(b) adding sulphuric acid to calcium hydroxide

(c) heating gypsum to a very high temperature

(d) heating gypsum to 100° C

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Answers Key:

Generic 2

5 x 2 = 10

The chemical formula of baking powder is sodium hydrogen carbonate \((NaHCO_3).\) while, that of washing soda is sodium carbonate carbonate on heating gives \(CO_2\) gas which will turn lime water milky whereas no such gas is obtained from sodium carbonate.

\(2NaHCO_3\xrightarrow {Heat}Na_2CO_3+H_2O+CO_2\)
\(NA_2CO_3.10H_2O\xrightarrow {Heat}Na_2CO_3+10H_2O\)

Commonly used compounds for making chalks and other pottery articles is plaster of paris. Its chemical formula is \((CaSO_4)_2.{1\over2}2H_2O\) onn partical losing water of crystallization by controlled heating of crystallization by controlled heating \(120^o-130^oC.\) When \(CaSO_4.2H_2O\) is strongly heated it loses whole of water of crystallisation and gives anhydrous calcium sulphate. Thus 'x' is \(CaSO_4.2H_2O\) is strongly heated it loses whole of water of crystallisation and gives anhydrous calcium sulphate. Thus 'x' is \(CaSO_4.2H_2O;\) y is \(CaSO_4.{1\over2}H_2O\) and 'z' is \(CaSO_4.\)

\(2CaSO_4.2H_2O\xrightarrow{heat/120^o-130^o\ C}(CaSO_4)_2.{1\over2}H_2O+{3\over 2}H_2O(g)\)

\(2CaSO_4.2H_2O\xrightarrow{heat/>130^oC}CaSO_4\)

The conduction of electricity in the two cases is different. Metals conduct electricity due to the mobile electrons present on their surfaces whereas ionic compounds conduct electricity due to the movement of ions either in molten state or in aqueous solution. Ionic solids do not conduct electricity because ions do not move in solid state.

An acid dissociates into hydronium ions (H₃O⁺) and anions when dissolved in water. When a solution is diluted, the volume of the solution increases but the number of ions remains the same, so concentration of hydronium ions (H₃O⁺) per unit volume decreases.

Curd and sour substances contain acids which react with copper and brass to form certain salts that are poisonous in nature and can cause food poisoning. Hence, sour substances like curd, pickles etc., should not be kept in brass and copper vessels.

Generic 3

3 x 3 = 9

(i) Alkali. e.g., NaOH (Sodium hydroxide).
(ii) Tooth decay starts when the pH of the mouth is lower than 5·5.It can be prevented by using tooth pastes which are generally basic.
(iii) Bee-sting has acid that causes pain and irritation. Baking soda is alkaline, neutralises the acid and gives relief.

(i) The raw materials used in the manufacture of sodium carbonate by Solvay process are calcium carbonate \((CaCO_3)\), ammonia gas \((NH_3)\), and sodium chloride solution \((NaCl)\).

(ii) Sodium hydrogen carbonate formed during Solvay process is separated from a mixture of \(NH_4Cl\) and \(NaHCO_3\) by the method of filtration.

(iii) Sodium carbonate is obtained from sodium hydrogen carbonate by heating it and then adding calculated amount of water into its.

Dilution of a concentrated acid is a highly exothermic reaction and a lot of heat is generated. Care must be taken while mixing concentrated acid with water. The acid must always be added slowly to water with constant stirring. If water is added to the concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.

Multiple Choice Question

5 x 1 = 5

(d)
weak acid and strong base

10.

11.

(d)
(i) and (iv)

12.

(d)
16 ml

13.

(b)
HCl

Generic 5

1 x 5 = 5

14.

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.

\(\underset{Plaster\ of\ Paris}{CaSO_4.{1\over 2}H_2O}+1{1\over2}{H_2O}\rightarrow \underset{Gypsum}{CaSO_4.2H_2O}\)

Passage Based Questions

1 x 1 = 1

15.

(a) The bulb will not glow
(b) Glucose will not dissociate into ions and the bulb will not glow.
(c) The hydrogen ions and chloride ions.
(d) The molten sodium chloride will allow the electricity to pass as it will dissociate into ions.

Data Based Questions

1 x 1 = 1

16.

(a) NH₄Cl in its solution dissociates as weak base, NH₄OH and strong acid, HCl. Thus, the solution is acidic and hence pH of solution is less than 7.
(b) NH₄SO₄ in its solution dissociates as strong acid, H₂SO₄ and weak base NH₄OH. Thus, it is acidic in nature.
(c) (i) HCI (d) (ii) CO₂

Assertion and reason

1 x 1 = 1

17.

(b) If both assertion and reason are true but reason is not a correct explanation of assertion.

Case Study Questions

2 x 4 = 8

18.

(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)
\({ (v) }(\mathrm{a}): \mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Cl}_{2} \longrightarrow \mathrm{CaOCl}_{2}+\mathrm{H}_{2} \mathrm{O}\)

19.

(i) (d): Gypsum is CaSO₄·2H₂Oand plaster of Paris is CaSO₄\(\frac{1}{2}\) H₂O. Difference in number of water molecules \(=\frac{3}{2}\).
(ii) (c): Plaster of Paris is hardened by combining with water.
(iii) (c): Dead burnt plaster is CaSO₄ (anhydrous calcium sulphate).
(iv) (d): Gypsum: CaSO₄ ·2H₂O Plaster of paris: CaSO₄ ·1/2H₂O
(v) (d): Gypsum on heating upto lOO°C gives plaster of Paris.
\(\begin{array}{c} \mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O} \stackrel{100^{\circ} \mathrm{C}}{\longrightarrow} \mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}+1 \frac{1}{2} \mathrm{H}_{2} \mathrm{O} { } \end{array}\)
Gypsum Plaster of Paris

CBSE 10th Science Acids, Bases and Salts Sample Question Papers Study Material - QB365 Set A

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Std: 10th Standard CBSE - Science

chapter: Acids, Bases and Salts - Sample Question Papers

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