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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
Limestone rock is the commonest form of calcium carbonate which also occurs with ____ carbonate as dolomite.A. BeB. SrC. BaD. Mg |
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Answer» Correct Answer - D Dolomite is `MgCO_(3).CaCO_(3)` |
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| 102. |
Calcium carbonate, commonly called limestone, is prepared by passing `CO_(2)(g)` throughA. `CaCI_(2)`B. `Ca(OH)_(2)`C. `Ca(HCO_(3))_(2)`D. `CaSO_(4)` |
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Answer» Correct Answer - B `Ca(OH)_(2)(aq.)+CO_(2)(g)toCaCO_(3)(s)+H_(2)O(l)` it is also obtained by the addition of sodium carbonate to calcium chloride: `CaCl_(2)+Na_(2)CO_(3)toCaCO_(3)+2NaCl` |
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| 103. |
How calcium hydroxide is prepared? |
| Answer» Calcium hydroxide is prepared by adding water to quick lime (CaO). | |
| 104. |
Why `CO_(2)` is removed when `CaCO_(3)` is heated in a rotary kiln? |
| Answer» The carbon dioxide is removed to enable the reaction to proceed to completion | |
| 105. |
Quick lime is prepared on a commercial scale by heating ____ in a rotary kiln at 1070-1270 K.A. `CaSO_(4)`B. `Ca(NO_(3))_(2)`C. `CaCO_(3)`D. `Ca(OH)_(2)` |
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Answer» Correct Answer - C `CaCO_(3)overset(Delta)hArrCaO+CO_(2)` |
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| 106. |
How flame test helps in distinguishing alkali metals? |
| Answer» Alkali metals give characteristic colour on flame, which helps in distinguishing them. | |
| 107. |
Which of the following is incorrect about the carbonates of alkaline earth metals ?A. They are insoluble in water.B. They are obtained as white precipitates when calculated amount of `CO_(2)` is passed through the solution of group 2 hydroxides.C. They are precipitated when sodium or ammonium carbonate solution is added to an aqueous solution of water soluble salt of group 2 elements.D. All the carbonates are ionic. |
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Answer» Correct Answer - D All the carbonates are ionic, but `BeCO_(3)` is unusual because it contains the hydrated `[Be(H_(2)O)_(4)]^(2+)` rather than `Be^(2+)` (2) `M(OH)_(2)(aq.)+CO_(2)(g)toMCO_(3)(s)+H_(2)O(l)` (3) `CaCl_(2)(aq.)+Na_(2)CO_(3)(aq.)toCaCO_(3)(s)+2NaCl(aq.)` Bryllium carbonate is prone to hydrolysis as it contains the hydrated ion `[Be(H_(2)O)_(4)]^(2+)` rather than `Be^(2+)` hence it can be precipitated only in an atmosphere of `CO_(2)`. `BeCO_(3)+4H_(2)Ounderset("Presence of "CO_(2))overset("Absence of "CO_(2))hArr[Be(H_(2)O)_(4)]^(2+)+CO_(3)^(2-)` |
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| 108. |
Because it is cheap (a byproduct of the Solvay process) and deliquescent, anhydrous `CaCI_(2)` is often used to dry gases and organic liquids. However, it cannot be used to dry ammonia and ethanol since it forms complexes having the respective formulasA. `CaCI_(2).8NH_(3) and CaCI_(2).4C_(2)H_(5)OH`B. `CaCI_(2).4NH_(3) and CaCI_(2).4C_(2)H_(5)OH`C. `CaCI_(2).8NH_(3) and CaCI_(2).8C_(2)H_(5)OH`D. `CaCI_(2).4NH_(3) and CaCI_(2).8C_(2)H_(5)OH` |
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Answer» Correct Answer - A The additive compound with `C_(2)H_(5)OH` is called alcoholate. |
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| 109. |
Why potassium carbonate `(K_(2)CO_(3))` cannot be prepared by Solvay-ammonia process ? |
| Answer» Solvay process cannot be used to prepare potassium carbonate. This is because unlike sodium bicarbonate, potassium bicarbonate is fairly soluble in water and does not precipitate out. | |
| 110. |
Why is `Li_(2)CO_(3)` decomposed at a lower temperature whereas `Na_(2)CO_(3)` at higher temperature? |
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Answer» As we move down the alkali metal group, the electropositive character increases. This causes an increase in the stability of alkali carbonates. However, lithium carbonate is not so stable to heat. This is because lithium carbonate is covalent. Lithium ion, being very small in size, polarizes a large carbonate ion, leading to the formation of more stable lithium oxide. `Li_(2)CO_(3)overset(Delta)rarrLi_(2)O+CO_(2)` Therefore, lithium carbonate decomposes at a low temperature while a stable sodium carbonate decomposes at a high temperature. |
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| 111. |
Why Beryllium and magnesium do not impart colour to the flame? |
| Answer» The electrons in beryllium and magnesium are strongly bound and do not get excited by the flame, therefore these two do not impart colour to the flame. | |
| 112. |
How beryllium hydride is different from the hydrides of other members of group 2? |
| Answer» Beryllium hydride is covalent and polymeric in nature whereas other hydrides are ionic in nature. | |
| 113. |
Except for lithium, alkali metals form their hydrides at what temperature. |
| Answer» Correct Answer - About 673K. | |
| 114. |
An element of group 2 forms covalent oxide which is amphoteric in nature and dissolves in water to give an amphoteric hydroxide. Identify the element and write chemical reactions of the hydroxide of the element with an alkali and an acid. |
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Answer» The alkaline earth metals burn in oxygen to form monoxide `MO.BeO` is essentially covalent in nature, other being ionic in nature. `BeO` is amphoteric while other oxides are basic in nature and react with water to form sparingly soluble hydroxides. `BeO` dissolves both in acid and alkalis to give salt and is amphoteric. `BeO +H_(2)O rarr underset("Beryllium hydroxide")(Be(OH)_(2))` `Be(OH)_(2)` is an amphoteric hydroxide, dissolving in both acids and alkalies. with alkalies it dissolve to form the tetrahydroxidoberyllate `(Z^(-))` anion with sodium hydroxide solution. `2NaOH(aq)+Be(OH)_(2)(s)rarr underset("Sodium tetra hydroxidoberyllate")(Na_(2)Be(OH)_(4)(aq))` With acids, it forms beryllium salts. `Be(OH)_(2)+underset("Sulphuric acid")(H_(2)SO_(4))rarr underset("Beryllium sulphate")(BeSO_(4))+2H_(2)O` |
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| 115. |
"Electron" is an alloy ofA. Mg and FeB. Mg and AlC. Mg and ZnD. Mg and Ni |
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Answer» Correct Answer - C Electron, an alloy of `Mg(95%),Zn(4.5%)`, and Cu (0.5%), is used in the construction of aircragts. |
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| 116. |
What happens when a. Sodium metal is dropped in water? b. Sodium metal is heated in free supply of air? c. Sodium peroxide dissolves in water? |
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Answer» (i) When Na metal is dropped in water It reacts violently to form sodium hydroxide and hydrogen gas. The chemical equation involved in the reaction is: `2Na_((s))+2H_(2)O_((l)) rarr 2NaOH_((aq))+H_(2(g))` (ii) On being heated in air, sodium reacts virorously wiht oxygen to form sodiu peroxide the chemical equation involved in the reaction is: `2Na_((s))+O_(2(s))rarr Na_(2)O_(2(s))` (iii) When sodium peroxide is dissolved in water it is readily hydrolysed to form sodium hydroxide and water. The chemical equation involved in the reaction is: `Na_(2)O_(2(s))+2H_(2)O_((l)) rarr 2NaOH_((aq))+H_(2)O_(2(aq))` |
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| 117. |
A certain compound X impats golden yellow flame. Whenzinc powder is heated with concenrated solution of X, `H_(2)` gas is evolved. X combines with `CO_(2)` to give a salt Y. Y is a hydrated salt which on reaction with HCl or ecess of `CO_(2)` gives another salt Z which is an important part of baking powder. identify X, Y and Z.A. `X-NaOH,Y-Na_(2)CO_(3),Z-NaHCO_(3)`B. `X-HCl, Y-NaOH,Z-NaHCO_(3)`C. `X-KOH,Y-K_(2)CO_(3),Z-KHCO_(3)`D. `X-NaCl,Y-Na_(2)CO_(3),Z-NaOH` |
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Answer» Correct Answer - A `Zn+underset((X))(2NaOH) to Na_(2)ZnO_(2)+H_(2)` `underset((X))(2NaOH)+CO_(2)tounderset((Y))(Na_(2)CO_(3))+H_(2)O` `underset((Y))(Na_(2)CO_(3))+HCl to underset((Z))(NaHCO_(3))+NaCl` ltBrgt `underset((Y))(Na_(2)CO_(3))+CO_(2)+H_(2)O to underset((Z))(2NaHCO_(3))` |
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| 118. |
A white solid X reacts with dil. HCl to give colourless gas which is used in fire extinguishers. The solid X isA. NaClB. `CH_(3)COONa`C. `Na_(2)CO_(3)`D. `naHCO_(3)` |
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Answer» Correct Answer - D `underset((X))(NaHCO_(3))+HCl to NaCl+H_(2)O+CO_(2)` |
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| 119. |
Lime water is an aqueous solution ofA. `MgSO_(4)`B. `Ca(OH)_(2)`C. `CaCO_(3)`D. `CaSO_(4)` |
| Answer» Correct Answer - B | |
| 120. |
Which of the following metals is most commonly used I photochemical cells?A. LithiumB. CalciumC. CaesiumD. Fracium |
| Answer» Correct Answer - C | |
| 121. |
Which substance can be used for purification of sugar?A. `CaCO_(3)`B. `Na_(2)CO_(3)`C. `CaHCO_(3)`D. `Ca(OH)_(2)^(-)` |
| Answer» Correct Answer - D | |
| 122. |
While purification of NaCl, why only crystal of pure NaCl separate out? |
| Answer» Crystal of pure sodium chloride separate out because calcium and magnesium chloride are more soluble than sodium chloride and remain in solution. | |
| 123. |
Which metal is used to remove air from vacuum tube? |
| Answer» Correct Answer - Calcium and barium. | |
| 124. |
State as to why (a) a solution of `Na_(2)CO_(3)` is alkaline ? (b) alkali metals are prepared by electrolysis of their fused chlorides? (c) sodium is found to be more useful than potassium ? |
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Answer» (a) When sodium cabonate is added to water, it hydrolyses to give sodium bicarbonate and sodium hydroxide (a strong base) As a result, the solution becomes alkaline `Na_(2)CO_(3)+H_(2)Orarr NaHCO_(3)+NaOH` (b) It is not possible to prepare alkali metals by the chemical reduction of their oxides as they themselves are very strong reducing agents. They cannot be prepared by displacement reactions either (wherein one element is displaced by another). This is because these elements are highly electropositive. Neither can electrolysis of aqueous solutions be used to extract these elements. this is because the liberated metals react with water Hence, to overcome these difficulties, alkali metals are usually prepared by the electroysis of their fused chlorides. (c) Blood plasma and the interstitial fluids surrounding the cells are the regions where sodium ions are primarily found . Potassium ions are located within the cell fluids Sodium ions are involved in the transmission of nerve singnals, in regulating the flow of water across the cell membranes, and in transporting sugars and amino acids into the cells. Hence, sodium is found to be more useful than potassium. |
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| 125. |
Fused `BeF_(2)` isA. ionicB. covalentC. both ionic and covalentD. a polymeric compound |
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Answer» Correct Answer - B All the halides of bryllium are covalent in nature due to the high polarizing power of `Be^(2+)` ion on account of high charge density. |
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| 126. |
What products are formed on thermal decomposition of `(NH_(4))_(2)BeF_(4)`? |
| Answer» `(NH_(4))_(2)BeF_(4) overset(Delta)toBeF_(2)+2NH_(4)F`. | |
| 127. |
On dissolving moderate amount of sodium metal in liquid ammonia at low temperature, which of the following does not occur ?A. Blue colored solution is not obtained.B. `Na^(+)` ions are formed in the solution.C. Liquid `NH_(3)` remains diamagnetic.D. Liquid `NH_(3)` becomoes a good conductor of electricity. |
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Answer» Correct Answer - C Solution of Na metal in liquid `NH_(3)` consists of solvated `Na^(+)` ions solvated electrons. Due to the presence of solvated electrons, liquid `NH_(3)` is no longer diamagnetic. If becomes paramagnetic: `Na+(x+y)NH_(3)rarrNa^(+)(NH_(3))+e^(-)(NH_(3))_(y)`. |
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| 128. |
Which of the alkali metals has the lowest density ?A. NaB. KC. RbD. Cs |
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Answer» Correct Answer - B As we move down the group, both the atomic mass and atomic size increase. But the increase in atomic mass more than compensates the increase in size. Consequently, the densities of alkali metlas increase from Li to Cs with deviation at K which is lighter than Na due to an abnormal deviation at K which is lighter than Na due to an abnormal increase in atomic size of K on account of the d-subshell. |
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| 129. |
Which of the following has the lowest density?A. BeB. MgC. CaD. Sr |
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Answer» Correct Answer - C The densities of alkaline earth metals do not show any regular trend with increasing atomic number. The density of these metals first decreases from Be to Ca (due to decrease in the packing of atoms in their solid lattice) and then increases form Ca to Ba. `Ra gt BA gt Sr gt Be gt Mg gt Ca` |
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| 130. |
Which of the following will have lowest value of `K_(sp)` at room temperature?A. `Be(OH)_(2)`B. `Mg(OH)_(2)`C. `Ca(OH)_(2)`D. `Ba(OH)_(2)` |
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Answer» Correct Answer - A `Be(OH)_(2)` is least soluble in water hence, it will have lowest value of `K_(sp)`. `Be(OH)_(2)hArr Be^(2+)+2OH^(-)` `K_(sp)=[Be^(2+)][OH^(-)]^(2)` |
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| 131. |
Which of the following has the highest boiling point?A. BeB. MgC. CaD. Sr |
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Answer» Correct Answer - A In general, it decreases on moving down the group but the trend is not systematic: `Be gt Ba gt Ra gt Ca gt Sr gt Mg` |
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| 132. |
Discuss the general characteristics and gradation in properties of alkaline earth metals. |
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Answer» General characteristics of alkaline earth metals are as follows. (i) The general electronic configuration of alkaline earth metals is [noble gas] `ns^(2)`. (ii) These metals lose two electrons to acquire the nearest noble gas configuration. Therefore, their oxidation state is `+2`. (iii)These metals have atomic and ionic radii smaller than that of alkali metals. Also, when moved down the group, the effective nuclear charge decreases and this causes an increase in their atomic radii and ionic radii. (iv)Since the alkaline earth metals have large size, their ionization enthalpies are found to be fairly low. However, their first ionization enthalpies are higher than the corresponding group 1 metals. (v) These metals are lustrous and silvery white in appearance. They are relatively less soft as compared to alkali metals. (vi)Atoms of alkaline earth metals are smaller than that of alkali metals. Also, they have two valence electrons forming stronger metallic bonds. These two factors cause alkaline earth metals to have high melting and boiling points as compared to alkali metals. (vii) They are highly electropositive in nature. This is due to their low ionization enthalpies. Also, the electropositive character increases on moving down the group from Be to Ba. (viii) Ca, Sr, and Ba impart characteristic colours to flames. Ca – Brick red Sr – Crimson red Ba – Apple green In Be and Mg, the electrons are too strongly bound to be excited. Hence, these do not impart any colour to the flame. The alkaline earth metals are less reactive than alkali metals and their reactivity increases on moving down the group. Chemical properties of alkaline earth metals are as follows. (i) Reaction with air and water: Be and Mg are almost inert to air and water because of the formation of oxide layer on their surface. (a) Powdered Be burns in air to form BeO and `Be_(3)N_(2)`. (b) Mg, being more electropositive, burns in air with a dazzling sparkle to form MgO and `Mg_(3)N_(2)`. (c) Ca, Sr, and Ba react readily with air to form respective oxides and nitrides. (d) Ca, Ba, and Sr react vigorously even with cold water. (ii) Alkaline earth metals react with halogens at high temperatures to form halides. `M+X_(2) rarr MX_(2)(X=F, Cl, Br, I)` (iii) All the alkaline earth metals, except Be, react with hydrogen to form hydrides. (iv) They react readily with acids to form salts and liberate hydrogen gas. `M+2HCl rarr MCl_(2)+H_(2(g)) uparrow` (v) They are strong reducing agents. However, their reducing power is less than that of alkali metals. As we move down the group, the reducing power increases. (vi) Similar to alkali metals, the alkaline earth metals also dissolve in liquid ammonia to give deep blue coloured solutions. `M+(x-y)NH_(3)rarr [M(NH_(3))_(x)]^(+2)+2[e(NH_(3))_(y)]^(-)` |
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| 133. |
Which of the following does not show the amomalous behaviour of lithium?A. Lithium reacts with nitrogen to form a nitrideB. Lithium carbonate decomposes on heatingC. Lithium nitrate gives `NO_(2)` on heatingD. lithium is the strongest reducing agent. |
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Answer» Correct Answer - D All alkali metals are strong reducing agents. |
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| 134. |
Anomalous Behaviour Of Lithium |
| Answer» It show anomalous behaviour due to the exceptionally small size of its atom and ion, and high polarising power (i.e., charge/radius ratio) | |
| 135. |
Anomalous Behaviour Of Beryllium |
| Answer» Beryllium does not exhibit coordination number more than four as in its valence shell, there are only four orbitals. The remaining members of the group can have a coordination number of six by making use of d-orbitals. | |
| 136. |
Which of the following is incorrect about sodium hydroxide ?A. It is a white, translucent crystalline solid.B. It is highly soluble in water to give a strong alkaline solution which is bitter in taste, corrosive, and soapy to touch.C. Crystals of NaOH are hygroscopic.D. It reacts with the `CO_(2)` in the atmosphere to form `Na_(2)CO_(3)`. |
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Answer» Correct Answer - C Crystals of NaOH are highly deliquescent i.e., have the property of picking up moisture from thhe air to such an extent that they dissolve in it. Thus NaOH becomes liquid on exposure to air. |
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| 137. |
Which of the following is incorrect for both Be and Al?A. Carbides of both the metals react with water liberating `C_(2)H_(2)` gas.B. Oxides and hydroxides of both Be and Ajl are amphoteric and dissolve in NaOH solution as well as ydrochloric acid solution.C. Oxides of both the metals are hard, high-melting insoluble solids.D. Salts of both the metals form hydrated ions in aqueous solution. |
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Answer» Correct Answer - A Carbides of both the metsls react with water liberating `CH_(4)` gas `Be_(2)C+4H_(2)Orarr2Be(OH)_(2)+CH_(4)` `Al_(4)C_(3)+12H_(2)Orarr4Al(OH)_(3)+3CH_(4)` |
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| 138. |
Milk of lime reacts with chlorine to form ________, a constituent of bleaching powder.A. `Ca(OCI)_(2)`B. `Ca(CIO_(2))_(2)`C. `Ca(CIO_(3))_(2)`D. `Ca(CIO_(4))_(2)` |
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Answer» Correct Answer - A `2Ca(OH)_(2)+2Cl_(2)rarrCaCl_(2)+Ca(Ocl)_(2)+2H_(2)O` |
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| 139. |
Bleaching powder is prepared by passing chlorine intoA. `Ca(OH)_(2)`B. CaOC. `CaCI_(2)`D. `CaCO_(3)` |
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Answer» Correct Answer - A `3Ca(OH)_(2)+2Cl_(2)toCa(Ocl)_(2).Ca(OH)_(2).CaCl_(2).2H_(2)O` though bleaching powder is often written as `Ca(OCl)_(2)`, it is really a mixture. |
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| 140. |
Which of the following changes occur when an excess of `CO_(2)(g)` is passed into a clear solution of limewater ?A. A white precipitate of `CaCO_(3)` is formed.B. A white precipitate of `CaCO_(3)` is formed initially which changes into soluble `CA(HCO_(3))_(2)` on passing excess `CO_(2)` gas.C. A white precipitate of `Ca(HCO_(3))_(2)` is formed.D. A white precipitate of both `CaCO_(3) "and" Ca(HCO_(3))_(2)` is formed. |
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Answer» Correct Answer - B When `CO_(2)(g)` is passed through lime water, it turns milky due to the formation of insoluble calcium carbonate: `Ca(OH)_(2)+CO_(2)toCaCO_(3)^(-)+H_(2)O` On passing excess of `CO_(2)(g)` the precipitate of `CaCO_(3)` dissolves to form soluble calcium bicarbonate. Hence the milkiness disappears. `CaCO_(3)+CO_(2)+H_(2)Otounderset("soluble")(Ca(HCO_(3))_(2))` If this clear solution of `Ca(HCO_(3))_(2)` is heated, the solution again turns milky due to te decomposition of calcium bicarbonate bakc to calcium carbonate: `Ca(HCO_(3))_(2)overset(Delta)toCaCO_(3)darr+CO_(2)+H_(2)O` |
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| 141. |
Which of the following sulphates crystallizes without water of crystallization ?A. `BaSO_(4)`B. `CaSO_(4)`C. `MgSO_(4)`D. `BeSO_(4)` |
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Answer» Correct Answer - A Beryllium magnesium, an calcium sulphates crystallize in hydrated from`BeSO_(4).4H_(2)O,MgSO_(4).7H_(2)O`, and `CaSO_(4).2H_(2)O` the sulphates of Ba and Sr crystallize without water of crystallization on account of the low charge density of `M^(2+)` ion. |
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| 142. |
Which of the following in incorrect ?A. Cement containing no iron is white.B. Cement containing excess amount of lime cracks during setting.C. Setting of cement is and endothermic process.D. Setting of cement is an example of hydration. |
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Answer» Correct Answer - C When mixed with water, the setting of cement, an exothermic process, taken place to give a hard mass. This is due to the hydration of molecules of the constituents andtheir rearrangement. The resulting hard mass has three-dimensional network structure involving `-Si-O-Si` and `-Si-O-Al-` chains. The purpose of adding gypsum is only to slow down the process of setting of the cement so that it gets sufficiently hardened. small amount of MgO (magnesia) and `Fe_(2)O_(3)` are required for imparting suitable color to cement. |
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| 143. |
The correct order of increasing thermal stability of `K_(2)CO_(3),MgCO_(3),CaCO_(3),` and `BeCO_(3)` isA. `K_(2)COltMgCO_(3)ltCaCO_(3)ltBeCO_(3)`B. `BeCO_(3)ltMgCO_(3)ltK_(2)CO_(3)ltCaCO_(3)`C. `BeCO_(3)ltMgCO_(3)ltCaCO_(3)ltK_(2)CO_(3)`D. `MgCO_(3)ltBeCO_(3)ltCaCO_(3)ltK_(2)CO_(3)` |
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Answer» Correct Answer - C Alkali metal carbonates are thermally more stable than alkaline arth metal carbonates. Among alkaline earth metal carbonates, thermal stability increases on moving down the group. |
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| 144. |
How would you explain the following observations ? (i) BeO is almost insoluble but `BeSO_(4)` is soluble in water (ii) BaO is soluble but `BaSO_(4)` is insoluble in water (iii) LiI is more soluble than KI in ethanol |
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Answer» (i) BeO is almost insoluble in water and `BeSO_(4)` is soluble in water `Be^(2+)` is a small cation with a high polarising power and `O^(2-)` is a small anion The size compatibility of `Be^(2+)` and `O^(2-)` is high. Therefore, the lattice energy released during their formation is also very high. When BeO is dissolved in water, the hydration enegy of its ions is not sufficient to overcome the high lattice energy. Therefore BeO is insoluble in water. On the other hand `SO_(4)^(2-)` ion is a large anion. Hence, `Be^(2+)` can easily polarise `SO_(4)^(2-)` ions, making `BeSO_(4)` unstable thus, the lattice energy at `BeSO_(4)` is not very high and so it is soluble in water (ii) BaO is soluble in water, but `BaSO_(4)` is not `Ba^(2+)` is a large cation and `O^(2-)` is a small anion. The size compatibility of `Ba^(2+)` and `O^(2-)` is not high. As a result, BaO is unstable. The lattice energy released during its formation is also not very large. It can easily be overcome by the hydration energy of the ions. Therefore, BaO is soluble in water. In `BaSO_(4), Ba^(2+)` and `SO_(4)^(2-)` are both large sized the lattice energy released is high Hence, it is not soluble in water (iii) LiI is more soluble than KI in ethanol. As a result of its small size, the lithium ion has a higher polarising power than the potassium ion. It polarises the electron cloud of the iodide ion to a much greater extent than the potassium ion. This causes a greater covalent character in LiI than in KI. Hence, LiI is more soluble in ethanol. |
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| 145. |
Why is `KO_(2)` paramagnetic ? |
| Answer» The superoxide `O_(2)^(-)` is paramagnetic because of one unpaired electron in `pi^(**)2p` molecular orbital | |
| 146. |
Why solubility of alkaline earth metal hydroxides increases from `Be(OH)_(2)` to `Ba(OH)_(2)`? |
| Answer» Among alkaline earth metal hydroxides the anion being common the cationic radius will infuence the lattice enthalpy Since lattice enthalpy decreases much more than the hydration enthalpy with increasing ionic size, the solubility increase as we go down the group. | |
| 147. |
Complete the following equations: (i) `Na_(2)O_(2)+2H_(2)O to underline((W))+H_(2)O_(2)` (ii) `2KO_(2)+2H_(2)O to underline((X))+underline((Y))+O_(2)` (iii) `Na_(2)O+CO_(2)to underline((Z))`A. W-4Na, X-`K_(2)O`,Y-`H_(2)O`,`Z-Na_(2)O_(2)`B. `W-4Na,X-K_(2)O,Y-H_(2)O_(2),Z-Na_(2)CO_(3)`C. `W-4NaOH,X-2KOH,Y-H_(2)O,Z-Na_(2)O_(2)`D. `W-2NaOH,X-2KOH,Y-H_(2)O_(2),Z-Na_(2)CO_(3)` |
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Answer» Correct Answer - D `Na_(2)O_(2)+2H_(2)Oto underset((W))(2NaOH)+H_(2)O_(2)` `2KO_(2)+2H_(2)O to underset((X))(2KOH)+underset((Y))(H_(2)O_(2))+O_(2)` `Na_(2)O+CO_(2) to underset((Z))(Na_(2)CO_(3))` |
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| 148. |
Which of the following is the most covalent in nature ?A. LiFB. LiCIC. LiBrD. LiI |
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Answer» Correct Answer - D The distortion of electron cloud of the anion by the cation is called polarization. The `Li^(+)` ion is very small in size and has high tendency to distort electron cloud around the halide ion. Because of the high polarization capability of `Li^(+)` ion, lithium halides are somewhat covalent. Since anion with large size can be easily distorted, among halides, LiI is the most covalent in nature. The order of covalent character is `LiI gt LIBr gt LiCI gt LiF` because larger the anion, greater is its polarizability. For the same reason, the dipole moment of LiI (0.25 D) is much leass than the excepted value (11.5 D) if it were 100% ionic. |
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| 149. |
Which of the following is known as sylvite ?A. KCIB. KFC. KBrD. KI |
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Answer» Correct Answer - A K occurs mainly as deposits of KCI (syvite), a mixture of KCI and NaCI (sylvinite), and the double salt `KCI.MgCI_(2).6H_(2)O` (carnallite). |
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| 150. |
Which of the following is correct for monoxides (normal oxides) of alkali metals ?A. They are ionic and strongly basic oxides.B. They are pure white solids.C. They have anti-fluorite structures.D. All of these. |
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Answer» Correct Answer - A They consist of `M^(+) "and" O^(2-)` ions. They react with water forming strong bases : `M_(2)O+H_(2)O to 2MOH` `Li_(2)O "and" Na_(2)O` are pure white solids, but surprisingly, `K_(2)O` is pale yellow, `Rb_(2)O` is bright yellow, and `Cs_(2)O` is orange. The crystal structures of `Li_(2)O, Na_(2)O,K_(2)O " and " Rb_(2)O` are anti-fluorite structures while `Cs_(2)O` has an anti-`CdCI_(2)` layer structure. |
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