ICSE Class 10 Chemistry Competency Focused Practice Questions Solution-Fill in the Blanks

ICSE Class 10 Chemistry Competency Focused Practice Questions Solution

II. Fill in the Blanks (1 mark each)

Question 39. [Mole Concept and Stoichiometry]
Fill in the blanks by choosing the correct options given in the brackets:

An aqueous solution of gas X turns red litmus blue, so it must contain (i)_______________
(hydrogen/ hydroxyl) ions. When this solution is added in excess to copper sulphate
solution, it turns to (ii) _____________ (deep blue/ pale blue) solution. Gas X is also a good
(iii) _____________ (oxidising/reducing) agent, which in excess reacts with a greenish-yellow gas
to form dense white fumes of (iv) _________________ (hydrogen chloride/ammonium chloride).

Answer:

(i) hydroxyl
(ii) deep blue
(iii) reducing
(iv) ammonium chloride

Explanation: Gas X is Ammonia (NH₃). Aqueous solution of ammonia is NH₄OH. When NH₄OH is added to copper sulphate solution, it turns to a bluish white precipitate of copper hydroxide is first formed. On adding excess ammonium hydroxide to the solution, the precipitate dissolves and a deep inky blue solution of tetrammine copper sulphate is formed.

Question 40. [Study of Compounds]
Ammonia can convert heated copper oxide to copper. This shows that ammonia is a _____________ (reducing agent/oxidising agent).

Answer: reducing agent

Explanation: The reaction is as follows:

3CuO + 2NH₃ → 3Cu + N₂ + 3H₂O

As ammonia removes oxygen from CuO, it acts as a reducing agent.

Question 41. [Mole Concept and Stoichiometry]
The number of hydrogen atoms present in 1 mole of sulphuric acid and 1 mole of
sulphurous acid are (X) and (Y), respectively. Relationship between X and Y is ___________ (X=Y / cannot compare X and Y).

Answer: X=Y

Explanation: In 1 mole of H₂SO₄, number of hydrogen atoms is 2. In 1 mole of H₂SO₃, number of hydrogen atoms is 2. Hence X = Y

Question 42. [Organic Chemistry]
Hydrocarbon X decolourises bromine in carbon tetrachloride, and hydrocarbon Y does
not decolourise bromine water. Both of the compounds burn with a sooty flame. The
molecular formula of X and Y is ______________ (C₅H₁₂ and C₄H₈ / C₅H₈ and C₄H₁₀).

Answer: C₅H₈ and C₄H₁₀

Explanation: Alkanes do not decolourise bromine water whereas Alkenes and Alkynes decolourises bromine in carbon tetrachloride. Hence, Y is alkane C₄H₁₀, (general formula of alkane is C_nH_2n+2) and X is C₅H₈ is alkyne (general formula of alkyne is C_nH_2n-2).

Question 43. [Organic Chemistry]
The number of chain isomers possible for an alkane with 5 carbon atoms are ____________
(3 / 4).

Answer: 3

Explanation: Isomers of pentane are: N-pentane. Isopentane and Neopentane.

Question 44. [Chemical Bonding]
Cations are (oxidised/ reduced) ions due to the ________________ (gain/loss) of
electrons by the neutral atom.

Answer: oxidised , loss

Explanation: Cations are formed by loss of electrons and loss of electrons is called oxidation.

Question 45. [Organic Chemistry]
If a hydrocarbon has the formula of C₅₀H₉₈, then it is likely to undergo ________________ a/an (addition/ substitution) reaction, and the hydrocarbon is a/an ________________
(saturated/ unsaturated hydrocarbon).

Answer: addition , unsaturated hydrocarbon

Explanation: In the hydrocarbon C₅₀H₉₈ , n= 50.

Using the general formula of alkyne C_nH_2n-2 , C₅₀H_{2 x 50 – 2} = C₅₀H₉₈ .

Hence, the given hydrocarbon is an alkyne. We know, alkyne is an unsaturated hydrocarbon and so undergoes addition reaction.

Question 46. [Periodic Properties and Variations of properties]
The atomic size of Boron is 0.88 A⁰, and that of nitrogen is 0.70 A⁰. Nitrogen lies to the
_____________ (left/ right) of Boron.

Answer: right

Explanation: Atomic size decreases from left to right in a period.

Question 47. [Electrolysis]
The ________________ (higher/ lower) is the position of the cation in the electrochemical series,
the greater the difficulty of it being discharged at the cathode.

Answer: higher

Explanation: According to the rules of preferential discharge of ions, the ions positioned lower in the electrochemical series will get discharged.

Question 48. [Study of Compounds]
The correct order of increasing volatility of the acids is _____________________.
(a) HCl < CH₃COOH < HNO₃
(b) CH₃COOH < HCl < HNO₃
(c) HNO₃ < HCl < CH₃COOH
(d) HCl < HNO₃< CH₃COOH

Answer: (b) CH₃COOH < HCl < HNO₃

Explanation: Remember that volatility is related to the boiling point; higher boiling points indicate lower volatility. Boiling point of CH₃COOH is 117.9°C, of HCl is 108.6°C and that of HNO₃ is 83°C.

Question 49. [Metallurgy]
Nikita wanted to gift her friend a decorative piece that is quite hard and strong, doesn’t
get corroded and can be polished. She selected a statue that matched her criteria as it
was made of an alloy whose main constituent was __________________.
(a) Cu
(b) Al
(c) Fe
(d) Zn

Answer: (a) Cu

Explanation: The decorative piece is made of Bronze, which is an alloy. The main constituent of Bronze is Copper.

I. Multiple Choice Question

II. Fill in the blanks

III. Match the following

IV. One Word Answer

V. Structural diagram

VI. IUPAC Names

VII. Very Short Answer Questions

VIII. Short Answer Questions

IX. Long Answer Questions