ICSE Class 10 Chemistry Competency Focused Practice Questions Solution-Multiple Choice Questions

ICSE Class 10 Chemistry Competency Focused Practice Questions Solution

I. Multiple Choice Questions (1 mark each)

Question 1. [Analytical Chemistry]

Ravi was asked to identify the cation present in the salt solution. He added one of the reagents given below and got a reddish-brown precipitate. The reagent that he used is:

(a) Silver nitrate solution
(b) Barium chloride solution
(c) Ammonium hydroxide
(d) Calcium chloride solution

Answer: (c) Ammonium hydroxide

Explanation: When Ammonium Hydroxide solution is added to the solution of the ferric chloride or any salt of ferric, ferric hydroxide will formed which is insoluble and forms reddish brown precipitate and remains insoluble in excess of ammonium Hydroxide.

Question 2. [Study of Compounds]

Which metal does not react with HCl to form a colourless, odourless gas which burns with a pop sound?

(a) Ca
(b) Mg
(c) Cu
(d) Zn

Answer: (c) Cu

Explanation: Copper is positioned lower than Hydrogen in the reactivity series of metals. Hence, it is less reactive than Hydrogen and cannot displace hydrogen from HCl to form hydrogen gas.

Question 3. [Study of Compounds]

Prateek added warm water to magnesium nitride, and a colourless gas evolved, which, when tested with phenolphthalein, turned it pink. The gas evolved is:

(a) Carbon dioxide
(b) Ammonia
(c) Nitrogen
(d) Hydrogen

Answer: (b) Ammonia

Explanation: Magnesium nitride when reacted with warm water produces Ammonia gas and magnesium hydroxide.

Mg₃N₂(s) + 6H₂O(l) → 3Mg(OH)₂(aq) + 2NH₃(g)

Question 4. [Organic Chemistry]

Which of the following statements about ethane is false?

(a) It is a saturated hydrocarbon.
(b) It undergoes a substitution reaction.
(c) It is a gas at ordinary temperatures.
(d) It has a triple bond between the carbon atoms.

Answer: (d) It has a triple bond between the carbon atoms.

Explanation: Ethane is an Alkane, which is a saturated hydrocarbon. It has a single bond between the carbon atoms.

Question 5. [Metallurgy]

Thermite mixture is used to weld the broken ends of the iron girders. This mixture consists of ferric oxide and aluminium powder, which, when heated, produces molten iron. In this reaction, the aluminium powder acts as a/an _________________ agent.

(a) oxidising
(b) reducing
(c) dehydrating
(d) corroding

Answer: (b) reducing

Explanation: The following is the equation of Thermite reaction:

Fe₂O₃ + 2Al → 2Fe + Al₂O₃

In the above reaction Aluminium removes Oxygen from ferric oxide. Thus it is acting as a reducing agent.

Question 6. [Electrolysis]

icse-class-10-chemistry-competency-focused-practice-questions-solution

The above diagram represents the electrolysis of acidulated water. The reaction occurring at the anode is:
(a) H₂SO₄ → 2H+ + SO₄^2-(b) H₂O → H+ + OH^–
(c) H + + e^– → H, 2[H] +2[H] → H₂
(d) OH^–– e^– → OH, [4OH] → 2H₂O + O₂

Answer: (d) OH^–– e^– → OH, [4OH] → 2H₂O + O₂

Explanation: Anode is a positive electrode. Hence, negative ion, OH^– migrates towards anode and changes to hydroxyl atom by donating an electron. 4 hydroxyl atoms thus formed make molecules of water and oxygen gas.

Question 7. [Period Properties and Variations of Properties]

With reference to the portion of the periodic table given above, identify the element having the largest atomic size:

(a) Li
(b) B
(c) K
(d) L

Answer: (b) B

Explanation: atomic size decreases from left to right in periods and increases from top to bottom in groups. Hence, B will have the largest atomic size.

Question 8. [Electrolysis]

The picture given below shows an apparatus that a teacher used for demonstrating the properties of ionic substances. The teacher heats a sample of lead bromide in a crucible which contains two electrodes which are part of the circuit shown. The bulb does not light up. What is the best explanation for this?

(a) The circuit is complete.
(b) Molten lead bromide does not conduct electricity.
(c) The sample of lead bromide was not heated up to the melting point by the teacher.
(d) The DC power supply was set up correctly.

Answer: (c) The sample of lead bromide was not heated up to the melting point by the teacher.

Explanation: If a circuit is complete, the bulb will light up. Molten lead bromide is a good conductor of electricity. According to the diagram given above, The DC power supply was set up correctly and that will light up the bulb. Hence options (a), (b) and (d) could not be the reasons for the bulb not lighting up. It is important to heat up the sample of lead bromide to the melting point. This is not clear from the diagram whether it was heated or not. Hence, option (d) is the best explanation for the bulb not lighting up.

Question 9. [Period Properties and Variations of Properties]

Element Y is in Group IIA of the Periodic Table. Y reacts with element Q to form an ionic compound. Which equation shows the process that takes place when Y forms ions?

(a) Y + 2e^– → Y²⁺
(b) Y – 2e^–→ Y^2-
(c) Y + 2e^– → Y^2–
(d) Y – 2e^– → Y²⁺

Answer: (d) Y – 2e^– → Y²⁺

Explanation: As element Y is in Group IIA of the Periodic Table, it is a metal. Metals always donate electrons to form a cation.

Question 10. [Electrolysis]

The diagram below shows a circuit used to electrolyse aqueous sodium argento cyanide. Which arrow indicates the movement of the silver ions in the electrolyte and of the electrons in the external circuit?

Silver ions Electrons
(a) 3 1
(b) 3 2
(c) 2 4
(d) 4 1

Answer: (d) 4 , 1

Explanation: Silver ions are positive ions, so they migrate towards cathode and in the external circuit, electrons move opposite to the direction of electric current. Hence, electrons will move from positive to negative terminal.

Question 11. [Mole Concept and Stoichiometry]

The relative atomic mass of nitrogen is 14, and that of hydrogen is 1. This means that (i) ___________ of nitrogen has the same mass as (ii) __________ of hydrogen.

	(i)	(ii)
(a)	An atom	28 molecules
(b)	An atom	7 molecules
(c)	A molecule	14 atoms
(d)	A molecule	7 atoms

Which words correctly complete the gaps?

Answer: (b) An atom / 7 molecules

Explanation: As atomic mass of hydrogen is 1, molecular mass of 1 hydrogen molecule (H₂) is 1 x2= 2. Hence, molecular mass of 7 molecules of hydrogen will be 7 x 2= 14, which is equal to atomic mass of Nitrogen.

Question 12. [Study of Compounds]

A student reacts copper turnings with cold dilute nitric acid in a test tube. He tests the gas given off with moist red and blue litmus paper. What is the name of the gas that evolved and what is the final colour of the litmus paper?

Gas Final colour of the litmus paper
(a) NO No change in blue and red litmus paper
(b) NO₂ Blue litmus turns red and no change in red litmus
(c) N₂ No change in blue and red litmus paper
(d) N₂O No change in blue and red litmus paper

Answer: (a) NO. No change in blue and red litmus paper

Explanation: The equation for reaction between copper turnings and cold dilute nitric acid is as follows:

3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O

Nitric oxide is a neutral gas. Hence, no change is observed in blue and red litmus paper.

Question 13. [Chemical Bonding]

Which element forms a stable ion with the same electronic configuration as argon?

(a) Magnesium
(b) Fluorine
(c) Chlorine
(d) Sodium

Answer: (c) Chlorine

Explanation: Every element in the periodic table wants to form a stable ion with the same electronic configuration as the nearest noble gas to it. Atomic number of chlorine is 17 and that of Argon is 18. Hence, chlorine forms a stable ion with the same electronic configuration as its nearest noble gas argon.

Question 14. [Organic Chemistry]

The diagram below represents the molecule of an organic compound. What is the name of this compound?

(a) Pentanol
(b) Butanol
(c) Butanoic acid
(d) Pentanoic acid

Answer: (b) Butanol

Explanation: 4 carbons in a row suggest the term butan. One hydroxyl atom suggests the suffix ‘ol’.

Question 15. [Electrolysis]

When a compound was electrolysed using inert electrodes, the gas released at the anode made a glowing splinter rekindle. The electrolyte that will not produce such gas observation at the anode is:
(a) diluted solution of NaCl.
(b) concentrated solution of NaCl.
(c) diluted solution of copper sulphate.
(d) acidified water.

Answer: (b) concentrated solution of NaCl.

Explanation: According to the rules of preferential discharge of ions, ions from the concentrated solution of electrolyte will discharge on the electrodes. Hence, if concentrated solution of NaCl is the electrolyte, then product at anode will be chlorine gas (Cl₂).

Question 16. [Organic Chemistry]

Which of the following chains of hydrocarbons undergoes two steps of reactions to become saturated?

Answer: (c)

Explanation: Ethyne has triple bond. First step of reaction will change it into Ethene (double bond) and then second step will change it into Ethane (single bond).

Question 17. [Study of Compounds]
Given below are four different illustrations of preparing hydrochloric acid drawn by
students. Which of these is the correct?

Answer: (a)

Explanation: The funnel is placed just touching the surface of water.

Question 18. [Organic Chemistry]
When two organic compounds A and B react together in the presence of conc.H₂SO₄, a
fruity smell evolved from one of the products. If A has the functional group [-O-H],
which of the following stands for the functional group of B?

Answer: (c)

Explanation: An alcohol and a carboxylic acid react together to form ester, which has a fruity smell. The functional group of alcohol is[-O-H]. Hence the other is carboxylic acid having functional group COOH.

Question 19. [Chemical Bonding]
Given below are four covalent compounds.
(A) H₂O
(B) CCl₄
(C) Cl₂
(D) NH₃

Which of the following represents the correct order when they are arranged in their
increasing number of covalent bonds?

(a) B < D <A < C
(b) A < C < D < B
(c) C < D < A < B
(d) C < A < D < B

Answer: (d) C < A < D < B

Explanation: Cl₂ has one covalent bond, H₂O has two, NH₃ has three and CCl₄ has four covalent bonds

Question 20. [Electrolysis]
The electrolytic cell used for the electrolysis of molten lead bromide is made of Silica.
Which of the following properties of silica that is the reason for it not having much
significance in the process of electrolysis?

(a) Hard and strong
(b) Non-conductor of electricity
(c) Non- reactive
(d) Withstands high temperature

Answer: (a) Hard and strong

Explanation: Silica is non-reactive, heat resistant and a poor conductor of electricity.

Question 21. [Organic Chemistry]
A distinctive reaction that takes place when ethanol is treated with acetic acid in the
presence of concentrated sulphuric acid to give a fruity smell.
P: The reaction is called esterification.
Q: The reaction is called hydration.

(a) Only P
(b) Only Q
(c) Both P and Q
(d) Both P and Q are wrong

Answer: (a) Only P

Explanation: In esterification reaction, ethanol is treated with acetic acid in the
presence of concentrated sulphuric acid to produce ester which has a fruity smell.

Question 22. [Study of Acids, Bases and Salts]
The pH of the soil is tested, and for the better growth of crops, slightly alkaline soil is
required. Which ion in the fertiliser will increase the alkalinity of the soil?

(a) Hydronium ion
(b) Hydroxyl ion
(c) Hydrogen ion
(d) Both hydroxyl and hydrogen

Answer: (b) Hydroxyl ion

Explanation: Hydroxyl ion is alkaline.

Question 23. [Chemical Bonding]
Ramu makes a detailed study on the values of electronegativity and the formation of
compounds. Accordingly, he draws the following conclusion:
The larger the electronegativity (EN) difference between the combining atoms, the more
ionic bonds will form.
If the EN difference is negligible, covalent bonds will form. So, which of the following
values refers to covalent bonds?
P: 3.0 and 3.0
Q: 0.9 and 3.0

(a) Only P
(b) Only Q
(c) Both P and Q
(d) Neither P nor Q

Answer: (a) Only P

Explanation: Since electronegativity difference is 0 (3 – 3= 0),therefore P refers to covalent bond.

Question 24. [Mole Concept and Stoichiometry]
10g of magnesium carbonate reacts completely with excess dilute hydrochloric acid.
What volume of carbon dioxide is formed at room temperature and pressure? [Mg=24,
C=12, O=16]
The equation for the reaction is:
MgCO₃ + 2HCl → MgCl₂ + H₂O + CO₂
(a) 2.8 dm³
(b) 2.6 dm³
(c) 2.2 dm³
(d) 2.4 dm³

Answer: (b) 2.6 dm³

Explanation: The given equation is:

MgCO₃ + 2HCl → MgCl₂ + H₂O + CO₂

Molecular mass of MgCO₃ = 24 + 12 +(16 x 3)

= 24 + 12 + 48 = 84 u

We know, At room temperature and pressure, one mole of any gas occupies approximately 24 dm³.

∴ 1mole of CO₂ will occupy 24 dm³.

Now, 84 g of MgCO₃ produces 22.4 dm³ of CO₂

∴ 10 g of MgCO₃ will produce = 22.4 x 10/84 = 2.6 dm³ of CO₂ .

Question 25. [Electrolysis]
The diagram shown is a wrong attempt to electroplate a pan with copper:

Which of the following could have been done to copper plate a pan?
(a) To change DC to AC.
(b) To change the electrolyte from copper sulphate to cobalt sulphate.
(c) Connect the pan to the negative electrode.
(d) To induce a higher current.

Answer: (c) Connect the pan to the negative electrode.

Explanation: The object to be electroplated is always connected to cathode (negative elecrode), as copper, being metal, has positive ions and positive ions will move towards negative electrode.

Question 26. [Metallurgy]
During the extraction of aluminium by Hall Heroult’s process, the carbon rods are
replaced continuously. This is because:
(a) It minimises heat loss by radiation.
(b) It enhances the mobility of ions.
(c) The carbon anode is consumed.
(d) It lowers the fusion point.

Answer: (c) The carbon anode is consumed.

Explanation: Oxygen is released, leading to the formation of carbon dioxide and during the oxidation of oxygen ions carbon anode is consumed.

Question 27. [Study of Acids, Bases and Salts]
Which of the following observations correctly shows the action of indicator on sodium
hydroxide solution?

	Indicator	methyl orange	phenolphthalein
(a)	P	orange to yellow	remains colourless
(b)	Q	orange to pink	remains colourless
(c)	R	orange to yellow	colourless to pink
(d)	S	remains orange	remains pink

Answer: (c) R

Explanation: Sodium hydroxide is a base. A base turns methyl orange to yellow colour and colourless phenolphthalin to pink.

Question 28. [Electrolysis]
When electrolysis of molten lead bromide is carried out, the products formed at the
respective electrodes are:

	At the positive electrode	At the negative electrode
(a)	Bromine	Lead
(b)	Bromine	Hydrogen
(c)	Lead	Bromine
(d)	Lead	Oxygen

Answer: (a)

Explanation: Bromine ions, being negative ions, will be discharged at the positive electrode. Lead ions, being positive ions, will be discharged at the negative electrode.

Question 29. [Organic Chemistry]
The following are the structural diagrams of certain hydrocarbons:

Which two structures are related to each other?

(a) A and B
(b) B and C
(c) C and D
(d) A and C

Answer: (d) A and C

Explanation: Molecular formula of both A and C are same, C₄H₁₀ . Both are isomers of Butane, A is isobutane (2 methyl propane) and C is n-butane (butane).

Question 30. [Chemical Bonding]
The electronic configuration of X is 2,8,6. It gains ‘Y’ electrons into its valence shell to
attain the nearest noble gas electronic configuration and gets converted to an ion Z.
X, Y, and Z, respectively, are:

(a) Sodium, one, electropositive
(b) Beryllium, two, electronegative
(c) Oxygen, six, electronegative
(d) Sulphur, two, electronegative

Answer: (d) Sulphur, two, electronegative

Explanation: Atomic number of Sulphur is 16. So, X is Sulphur. To become stable, sulphur will gain 2 electrons to have electronic configuration 2, 8, 8. As it will gain two electrons, it will become electronegative.

Question 31. [Periodic Properties and Variations of properties]
Which of the following arrangements is INCORRECT as per the property stated against
it?

(a) Li > Be > N > O (Metallic character)
(b) CI > F > Br >I (Electron gain enthalpy)
(c) O^2- > F^–> Mg ²⁺ >Na⁺ (Ionic radii)
(d) I > Br > CI > F (Number of shells)

Answer: (c) O^2- > F^–> Mg ²⁺ >Na⁺ (Ionic radii)

Explanation: Atomic radius decreases in a period from left to right. Hence the correct sequence will be Na⁺ > Mg ²⁺ > O^2- > F^–

Question 32. [Organic Chemistry]
Baking soda (NaHCO₃), when added to vinegar, evolves a gas. Which of these
statements is true about the evolution of gas?
I. It turns limewater milky.
II. It extinguishes the burning splinter.
III. It acts as a non-metallic oxide
IV. It has a pungent odour.

(a) I and IV
(b) I and II
(c) I, II and III
(d) III and IV [Recall & Understanding]

Answer: (c) I, II and III

Explanation: The equation for the reaction is as follows:

NaHCO₃ +CH₃COOH → CH₃COONa + H₂O + CO₂

The gas evolved is CO₂ , which is odourless.

Question 33. [Electrolysis]
The statements below show the results when three metal strips, P, Q, and R, are placed
in blue copper sulphate solution.
P- Solution turns green.
Q- Solution becomes colourless.
R- Solution remains blue.
Which of the following metals could be P, Q, and R?

(a) P-Al, Q-Zn, R- Fe
(b) P-Zn, Q-Fe, R- Ag
(c) P-Fe, Q-Zn, R-Ag
(d) P- Zn, Q-AI, R– Fe

Answer: (c) P-Fe, Q-Zn, R-Ag

Explanation: Fe with CuSO₄ produces FeSO₄ which is dirty green in colour. Zn with CuSO₄ produces ZnSO₄ which is colourless. Ag will not react with CuSO₄ , so the colour of CuSO₄ will remain blue.

Question 34. [Study of Compounds]

Study the above diagram and choose the correct option related to the content given
below:
Compound X reacts with ammonia in the combustion tube, which leaves a residue Y.
Identify X and Y, as well as the property Z of ammonia demonstrated in this particular
reaction.

(a) X= CuO, Y=black, Z = reducing property.
(b) X=PbO, Y = yellow, Z=oxidising property.
(c) X=CuO, Y =yellow, Z =oxidising property.
(d) X=PbO, Y=black, Z=reducing property.

Answer: (a) X= CuO, Y=black, Z = reducing property

Explanation: The reaction is as follows:

3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O

NH₃ removes oxygen from CuO displaying its reducing property.

Question 35. [Study of Compounds]
Assertion (A): Few drops of dilute acid is added to a solution of zinc sulphide, a
colourless gas is formed with a rotten egg odour.
Reason (R): Gas formed does not turn moist lead acetate paper silvery black.

(a) Both A and R are true.
(b) A and R are true, but R is the correct explanation of A.
(c) A is true, but R is not the correct explanation of A.
(d) Both A and R are false.

Answer: (c) A is true, but R is not the correct explanation of A.

Explanation: Hydrogen sulphide gas turns lead acetate paper silvery black.

Question 36. [Metallurgy]
Assertion (A): Hall Heroult’s process is used to get pure aluminium from its oxide.
Reason (R): Aluminium generally is not found in aluminium oxide form.

(a) Both A and R are correct.
(b) A is correct, but R is not a true explanation of A.
(c) A is correct, and R is a true explanation of B.
(d) Both A and R are incorrect.

Answer: (b) A is correct, but R is not a true explanation of A.

Explanation: The Hall-Heroult process is widely used in the extraction of aluminium. In Hall-Heroult’s process, pure Al₂O₃ is mixed with CaF₂ and Na₃AlF₆.

Because of its strong affinity for oxygen, aluminium is almost never found in the elemental state; instead it is found in oxides or silicates.

Question 37. [Organic Chemistry]
Assertion (A): Alkenes, alkynes and alkanes are examples of homologous series.
Reason (R): Organic compounds of the homologous series have similar structures but
different chemical properties.

(a) Both A and R are true.
(b) Both A and R are false.
(c) A is true but R is not the correct explanation of A.
(d) A is false but R is true.

Answer: (c) A is true but R is not the correct explanation of A.

Explanation: Compounds in the homologous series have same chemical properties and different physical properties.

Question 38. [Mole Concept and Stoichiometry]
Assertion (A): The atomic mass of oxygen is 16 a.m.u; therefore, its gram atomic
mass is 16g.
Reason (R): The atomic mass of an element expressed in grams is called gram atomic
mass.

(a) A is true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not a true explanation of A.
(c) Both A and R are false.
(d) R is false, but A is a true explanation.

Answer: (a) A is true, and R is the correct explanation of A.

Explanation: Definition of gram atomic mass is “the atomic mass of an element expressed in grams.”