CBSE Class 11 Chemistry - MCQ and Online Tests - Unit 10 - The s-Block Elements

CBSE Class 11 Chemistry – MCQ and Online Tests – Unit 10 – The s-Block Elements

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CBSE Class 11 Chemistry – MCQ and Online Tests – Unit 10 – The s-Block Elements

Question 1.
What happens when Calcium carbonate is heated to 1200 K?
(a) Carbon Monoxide
(b) Calcium hydroxide
(c) Calcium Oxide
(d) Both (2) and (3) are correct

Answer

Answer: (d) Both (2) and (3) are correct
Explanation:
Calcium carbonate is strongly heated until it undergoes thermal decomposition to form calcium oxide and carbon dioxide. The calcium oxide (unslaked lime) is dissolved in water to form calcium hydroxide (limewater).
CaCO₃ ? CaO + CO₂

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Question 2.
The salt that is added to table salt to make it flow freely in rainy season is
(a) KCl
(b) KI
(c) Ca₃(PO₄)₂
(d) Na₃PO₄

Answer

Answer: (c) Ca₃(PO₄)₂
Explanation:
Ca₃(PO₄)₂. Both Ca and P are needed by human beings. Also they prevent moisture absorbing power of other components such as MgCl₂, CaCl₂, CaSO₄ and MgSO₄ present in commercial sodium chloride.

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Question 3.
Alkali metals give a _________________when dissolved in liquid ammonia
(a) Deep blue solution
(b) Colourless
(c) Red colour
(d) None of the Above

Answer

Answer: (a) Deep blue solution
Explanation:
When an alkali metal is dissolved in liquid ammonia, it results in the formation of a deep blue coloured solution. The ammoniated electrons absorb energy corresponding to a red region of visible light. Therefore, the transmitted light is blue in colour.

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Question 4.
What are Oxo-Acids?
(a) Acid containing Oxygen
(b) Acid containing Sulphur
(c) Acid containing Carbon
(d) None of the Above

Answer

Answer: (a) Acid containing Oxygen
Explanation:
An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bond to oxygen that can dissociate to produce the H⁺ cation and the anion of the acid. e.g., carbonic acid, H₂CO₃ (OC(OH)₂; sulphuric acid, H₂SO₄ (O₂S(OH)₂).

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Question 5.
In curing cement plasters, water is sprinkled from time to time. This helps in
(a) Converting sand into silicic acid
(b) Keeping it cool
(c) Developing interlocking needle like crystals of hydrated silicates
(d) Hydrating sand and gravel mixed with cement.

Answer

Answer: (c) Developing interlocking needle like crystals of hydrated silicates
Explanation:
Water develops interlocking needle ­like crystals of hydrated silicates. The reactions involved are the hydration of calcium aluminates and calcium silicates which change into their colloidal gels.

At the same time, some calcium hydroxide and aluminium hydroxides are formed as precipitates due to hydrolysis. Calcium hydroxide binds the particles of calcium silicate together while aluminium hydroxide fills the interstices rendering the mass impervious

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Question 6.
The substance not likely to contain CaCO₃ is
(a) Dolomite
(b) A marble statue
(c) Calcined gypsum
(d) Sea shells.

Answer

Answer: (c) Calcined gypsum
Explanation:
The composition of gypsum is CaSO₄ ·2H₂O. It does not have CaCO₃

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Question 7.
Carnallite is the mineral of:
(a) Na
(b) Ca
(c) Mg
(d) None of the Above

Answer

Answer: (c) Mg
Explanation:
Carnallite is an evaporite mineral a hydrated potassium magnesium chloride. It is variably coloured yellow to white, reddish or blue. It occurs with a sequence of potassium and magnesium evaporite. It is an uncommon double chloride mineral that forms under specific conditions. It is an important source of potash.

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Question 8.
The wire of flash bulb is made up of:
(a) Mg
(b) Ag
(c) Cu
(d) Ba

Answer

Answer: (a) Mg
Explanation:
Magnesium metal is used for the preparation of the wire of flash bulb.

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Question 9.
The basic strength of which hydroxide is maximum
(a) LiOH
(b) NaOH
(c) Ca (OH)₂
(d) KOH.

Answer

Answer: (d) KOH.
Explanation:
The basic strength increases down the group and decreases along a period.

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Question 10.
The composition of Sorels cement is
(a) KCl × MgCl₂× 6H₂O
(b) MgCl₂ × 5MgO × (xH₂O)
(c) MgCO₃ × CaCO₃
(d) CaSO₄ × 2H₂O

Answer

Answer: (b) MgCl₂ × 5MgO × (xH₂O)
Explanation:
Mixture of MgCl₂ and MgO is called Sorels cement. It is MgCl₂ × 5MgO × (xH₂O)

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Question 11.
The hydration energy of Mg²⁺ is larger than that of
(a) A1³⁺
(b) Na⁺
(c) Be²⁶
(d) Mg³⁺

Answer

Answer: (b) Na⁺
Explanation:
Hydration energy depends on charge of ion and ionic radius. Higher the charge, greater the hydration energy. On the other hand, smaller the size, greater the hydration energy. Charge is considered first for comparison. Hence, Mg²⁺ has higher hydration energy than Na⁺.

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Question 12.
CsOH is
(a) Strongly basic
(b) Weakly basic
(c) Slightly acidic
(d) Amphoteric.

Answer

Answer: (a) Strongly basic
Explanation:
Caesium hydroxide or cesium hydroxide (CsOH) is a chemical compound consisting of caesium ions and hydroxide ions. It is a strong base (p_kb = -1.76), much like the other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

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Question 13.
Solvays process is used for the manufacture of :
(a) NaOH
(b) (Na₂CO₃. 10H₂O)
(c) K₂CO₃
(d) Na₂O₂

Answer

Answer: (b) (Na₂CO₃. 10H₂O)
Explanation:
The Solvay process or ammonia soda process is used for the manufacture of sodium carbonate
(Na₂CO₃. 10H₂O).

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Question 14.
Milk of lime reacts with chlorine to form ________, a constituent of bleaching powder.
(a) Ca(OCI)₂
(b) Ca(CIO₂)₂
(c) Ca(CIO₃)₂
(d) Ca(CIO₄)₂

Answer

Answer: (a) Ca(OCI)₂
Explanation:
Milk of lime reacts with chlorine to form bleaching powder.
2Ca(OH)₂ + 2Cl₂ ? CaCl₂ + Ca(OCl)₂ + 2H₂O

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Question 15.
The wire of flash bulb is made up of:
(a) Mg
(b) Ag
(c) Cu
(d) Ba

Answer

Answer: (a) Mg
Explanation:
Magnesium metal is used for the preparation of the wire of flash bulb.

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Question 16.
Usually CaCl₂ is preferred over NaCl for cleaning snow on roads particularly in very cold countries this is because
(a) NaCl makes the road slippery but CaCl₂ doesnot
(b) CaCl₂ is hygroscopic but NaCl is not
(c) CaCl₂ is less soluble in H₂O than NaCl
(d) eutectic mixtue of CaCl/H₂O freezes at -55°C while that of NaCl/H₂O freezes at -18°C

Answer

Answer: (d) eutectic mixtue of CaCl/H₂O freezes at -55°C while that of NaCl/H₂O freezes at -18°C
Explanation:
Eutectic mixture of CaCl₂/H₂O freezes at -55°C while that of NaCl/H₂O freezes at -18°C.

When added to ice. NaCl and CaCl₂ ionise into respective ions (Na⁺, Ca²⁺ & Cl^–) this leads to increase in the number of particles (ions). As CaCl₂ has greater number of ions, Increasing the number of particles /ions increases the vant hoff factor. Vant hoff factor is directly proportional to the depression in freezing point thus lowers the freezing point of ice causing preventing the formation of ice.

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Question 17.
CsOH is
(a) Strongly basic
(b) Weakly basic
(c) Slightly acidic
(d) Amphoteric.

Answer

Answer: (a) Strongly basic
Explanation:
Caesium hydroxide or cesium hydroxide (CsOH) is a chemical compound consisting of caesium ions and hydroxide ions. It is a strong base (p_kb = -1.76), much like the other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

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Question 18.
Which of the following metals is not manufactured by electrolysis?
(a) Na
(b) Mg
(c) Al
(d) Fe

Answer

Answer: (d) Fe
Explanation:
Method of extraction of a metal depends on the reactivity of the metal. Iron (Fe) is not manufacture by electrolysis. Moderately reactive metals like zinc and iron are extracted by reduction of their oxides using carbon.

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Question 19.
Which of the following alkali metals has the least melting point?
(a) Na
(b) K
(c) Rb
(d) Cs.

Answer

Answer: (d) Cs.
Explanation:
Atomic size increases as we move down the alkali group. As a result, the binding energies of their atoms in the crystal lattice decrease. Also, the strength of metallic bonds decreases on moving down a group in the periodic table. This causes a decrease in the melting point. Among the given metals, Cs is the largest and has the least melting point.

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Question 20.
The basic strength of which hydroxide is maximum
(a) LiOH
(b) NaOH
(c) Ca(OH)₂
(d) KOH.

Answer

Answer: (d) KOH.
Explanation:
The basic strength increases down the group and decreases along a period.

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