Q: HCl was passed through a solution of CaCl2 ,MgCl2 and NaCl. compound(s) crystallise(s)?

Since CalCl2 and MgCl2 are more soluble than NaCl, on passing HCl(g) through a solution containing CaCl2,MgCl2 and NaCl then NaCl crystallizes out.

Q: Which of the following is an amphoteric hydroxide?

Be(OH)2 amphoteric in nature, since it can react both with acid and baseBe(OH)2+2HCl→BeCl2+2H2O 2NaOH(aq)+Be(OH)2( s)→Na2[Be(OH)4](aq)

Q: Which of the following oxides is most acidic in nature?

BeO<MgO<CaO<BaO Basic character increases.So, the most acidic should be BeO. In fact, BeO is amphoteric oxide while other given oxides are basic.

Q: Among CaH2,BeH2,BaH2, the order of ionic character is :

For 2nd group hydrides, on moving down the group metallic character of metals increases so ionic character of metal hydride increases.Hence the option (3) should be correct option.

Q: Which of the following statements is false?

Monovalent sodium and potassium ions and divalent magnesium and calcium ions are found in large properties in biological fluids. There ions perform important biological functions such as maintenance of heart and nerve impulse.

Q: The product obtained as a result of a reaction of nitrogen with CaC2 is :

CaCN2 is not given in the option so it should be bonus

Q: Statement which are incorrect regarding Be?

Be has relatively high tendency to form complexes (high charge and small size).Example: :[Be(H2O)4]2+Most of the compound of Be are highly soluble in water due to high hydration energy of Be2+ except Be(OH)2.

Q: Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field?

Li+ being smallest, has maximum charge densitySo, Li+ is most heavily hydrated among all alkali metalions. Effective size of Li+ in aq solution is therefore,largest.Therefore, Moves slowest under electric field.

Q: On heating which of the following releases CO2 most easily?

Thermal stability orderK2CO3>Na2CO3>CaCO3>MgCO3 Therefore MgCO3 releases CO2 most easily.

Question 1

HCl was passed through a solution of CaCl2​ ,MgCl2​ and NaCl. compound(s) crystallise(s)?

Accepted Answer

Since CalCl2​  and MgCl2​ are more soluble than NaCl, on passing HCl(g) through a solution containing CaCl2​,MgCl2​ and NaCl then NaCl crystallizes out.

Question 2

Enzymes that utilize ATP in phosphate transfer require an alkaline earth metal (M) as the cofactor. M is :

Accepted Answer

All enzymes that utilize ATP in phosphate transfer require magnesium(Mg) as the co-factor.

Question 3

Which of the following is an amphoteric hydroxide?

Accepted Answer

Be(OH)2​ amphoteric in nature, since it can react both with acid and baseBe(OH)2​+2HCl→BeCl2​+2H2​O 2NaOH(aq)+Be(OH)2​( s)→Na2​[Be(OH)4​](aq)

Question 4

Which of the following oxides is most acidic in nature?

Accepted Answer

BeO<MgO<CaO<BaO Basic character increases.So, the most acidic should be BeO. In fact, BeO is amphoteric oxide while other given oxides are basic.

Question 5

Among CaH2​,BeH2​,BaH2​, the order of ionic character is :

Accepted Answer

For 2nd  group hydrides, on moving down the group metallic character of metals increases so ionic character of metal hydride increases.Hence the option (3) should be correct option.

Question 6

Which of the following statements is false?

Accepted Answer

Monovalent sodium and potassium ions and divalent magnesium and calcium ions are found in large properties in biological fluids. There ions perform important biological functions such as maintenance of heart and nerve impulse.

Question 7

The product obtained as a result of a reaction of nitrogen with CaC2​ is :

Accepted Answer

CaCN2​ is not given in the option so it should be bonus

Question 8

Statement which are incorrect regarding Be?

Accepted Answer

Be has relatively high tendency to form complexes (high charge and small size).Example: :[Be(H2​O)4​]2+Most of the compound of Be are highly soluble in water due to high hydration energy of Be2+ except Be(OH)2​.

Question 9

Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field?

Accepted Answer

Li+  being smallest, has maximum charge densitySo, Li+ is most heavily hydrated among all alkali metalions. Effective size of Li+  in aq solution is therefore,largest.Therefore, Moves slowest under electric field.

Question 10

On heating which of the following releases CO2​ most easily?

Accepted Answer

Thermal stability orderK2​CO3​>Na2​CO3​>CaCO3​>MgCO3​ Therefore MgCO3​ releases CO2​ most easily.

Question 11

What are the common physical and chemical features of alkali metals ?

Accepted Answer

Common physical features of alkali metals:(1) They are soft and can be easily cut.(2) They have silvery white appearance. They are light coloured.(3) Due to large atomic size, they have low density. On moving down the group the density increases with exception of K which has lower density than Na.(4) Due to weak metallic bonding, alkali metals have low melting and boiling points. (5) They provide characterisitc colour to flames.(6) They show photoelectric effect. On irradiation with lightCs and K lose electrons.Common chemical features of alkali metals:Due to low ionization enthalpy, akali metals have high reactivity. On moving down the group, the reactivity increases.(1) On reaction with water, oxides and hydroxides are formed. On moving down the group, the reaction becomes more and more vigorous.(2) On reaction with water, hydroxide and hydrogen are formed.2M+2H2​O→2MOH+H2​(3) On reaction with hydrogen, hydrides are formed.2M+H2​→MH(4) They directly combine with halogens to form ionic halides. Li is an exception.2M+Cl2​→2MCl, (M=Li,K,Rb,Cs)(5) They are strong reducing agents. On moving down the group, the reducing power increases with exception of Li. Due to high hydration energy, Li is the strongest reducing agent among alkali metals.(6) They dissolve in liquid ammonia. The solution is deep blue in colour due to presence of ammoniated electrons.

Question 12

Discuss the general characteristics and gradation in properties of alkaline earth metals.

Accepted Answer

General characteristics of alkaline earth metals:(1) They have valence shell electronic configuration of  ns2.(2) They lose two valence electron to form dipositive metal ions. Thus, they attain stable noble gas electronic configuration.(3) The atomic and ionic radii of alkaline earth metals are smaller than the atomic and ionic radii of alkali metals.(4) Due to large atomic size, the ionization enthalpy value of alkaline earth metals are very low. The first ionization enthalpy values are higher than those of alkali metals.(5) They have metallic luster and silvery white appearance. Compared to alkali metals, alkaline earth metals have lower softness.(6) The atomic size of alkaline earth metals is lower than that of alkali metals. Also the metallic bonds are stronger due to presence of 2 valence electrons. Hence, alkaline earths have higher melting and boiling points than alkali metals.(7) Due to lower ionization enthalpy values, the alkaline earths are highly electopositive in nature. On moving down the group, the electopositive nature increases from Be to Ba.(8) With exception of Be and Mg, the alkaline earths (Ca, Sr and Ba) provide characteristic colour to flame. Ca, Sr and Ba provide Brick red, Crimson red and Apple green colour to the flame respectively. Be and Mg cannot be excited in the flame as the electrons are tightly held.  The gradation in properties of alkaline earth metals:The chemical reactivity of alkaline earth metals is lower than the chemical reactivity of alkali metals. On moving down the group, the chemical reactivity increases.(1) Reaction with air and water: Be and Mg form an inert layer of oxide on their surface. Hence, they are inert to air and water.(i) In air, powdered Be burns to form its oxide and nitride.(ii) Mg burns in air with dazzling spark to form oxide and nitride.(iii) Ca, Sr and Ba readily react with air to form oxides and nitrides.(iv) Ca, Sr and Ba vigorously react with cold water.(2)  On reaction with halogen at high temperature, alkaline earths form halides.(3) On reaction with hydrogen, alkaline earths (except Be) form hydrides.(4) On reaction with acids, alkaline earths form salts and liberate hydrogen.(5) They act as strong reducing agents. They are weaker reducing agents than alkali metals. On moving down the group, the reducing ability increases.(6) They dissolve in liquid ammonia. The solution is deep blue in colour due to presence of ammoniated electrons.

Question 13

Why are alkali metals not found in nature?

Accepted Answer

Alkali metals have low ionization enthalpy values. Hence they readily lose their valence electrons and are highly reactive. Hence, in nature, they are not found in elemental state. In combined state, they are present in the form of halides, oxides, silicates, borates and nitrates.

Question 14

Find out the oxidation state of sodium in Na2​O2​.

Accepted Answer

Let x be the oxidation station of sodium in Na2​O2​.It contains a peroxide linkage in which each O atom has the oxidation number of -1.2x+2(−1)=0x=+1Thus, the oxidation state of sodium in Na2​O2​ is +1.

Question 15

Explain why is sodium less reactive than potassium.

Accepted Answer

Potassium has lower ionization enthalpy (496 kJ/mol) than sodium (520 kJ /mol).Thus, the ease with which K loses an electron is higher than the ease with which Na loses an electron. Hence, sodium is less reactive than potassium. The standard reduction potential of potassium (-2.925  V) is more negative than that of sodium (-2.714 V). This also indicates lower reactivity of sodium as compared to potassium.

Question 16

Compare the alkali metals and alkaline earth metals with respect to (i) ionisation enthalpy (ii) basicity of oxides and (iii) solubility of hydroxides.

Accepted Answer

(i) Ionization enthalpy:Alkaline earths have higher ionization enthalpy values than alkali metals. This is because the atomic size of alkaline earths is smaller than that of alkali metals. (ii) Basicity of oxides:On dissolution in water, the oxides of alkali metals and alkaline earth metals form basic hydroxides. The basicity of alkali metal oxides is higher than that of alkaline earth metal oxides due to lower ionization enthalpy of alkali metals than that of corresponding alkaline earths.  Due to this, the M-OH bond in alkali metal hydroxides can more easily ionize. (iii) Solubility of hydroxides:Alkaline earths have larger lattice energies than alkali metals due to small size and high charge. Hence, alkaline earth metal hydroxides have lower solubility than alkali metals.

Question 17

In what ways lithium shows similarities to magnesium in its chemical behaviour?

Accepted Answer

Chemical similarities between Li and Mg:(1) Their reaction with cold water is slow.(2) The solubility of the oxides of Li and Mg in water is low. At high temperature, the hydroxides decompose.2LiOHHeat​Li2​O+H2​OMg(OH)2​Heat​MgO+H2​O.(3) They form nitrides by reaction with nitrogen.6Li+N2​heat​2Li3​N3Mg+N2​heat​Mg3​N2​(4) They do not form peroxides or superoxies.(5) They form covalent carbonates which decompose on heating.Li2​CO3​heat​Li2​O+CO2​MgCO3​heat​MgO+CO2​(6) They do not form solid bicarbonates.(7) Their covalent chlorides are soluble in ethanol.(8) Their chlorides are deliquescent and crystallize from aqueous solution as hydrates such as LiCl2​.2H2​O and MgCl2​.8H2​O

Question 18

Explain why can alkali and alkaline earth metals not be obtained by chemical reduction methods?

Accepted Answer

Alkali and alkaline earth metals have high reduction potentials. Hence, they are very strong reducing agents. Hence, other reducing agents cannot reduce oxides or other compounds of alkali and alkaline earth metals. Hence, chemical reduction is not possible.

Question 19

Why are potassium and caesium used, rather than lithium used in photoelectric cells?

Accepted Answer

The ionization potentials of potassium and cesium are lower than that of lithium. On exposure to light, potassium and caesium easily emit electrons however lithium does not. Hence, potassium and caesium are used in the photoelectric cell.

Question 20

When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.

Accepted Answer

Different concentrations of alkali metals in liquid ammonia results in different colours. The dilute solutions are blue in colour due to presence of ammoniated electrons.  The concentrated solutions have copper bronze colour as  ammoniated metal ions are bound by free electrons.

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