Alkali metals Questions in English

(C) Sodium metal is highly reactive and reacts with alcohols to form sodium alkoxides and hydrogen gas.
$2C_2H_5OH + 2Na \to 2C_2H_5ONa + H_2$
Therefore,it cannot be stored in alcohol.

(A) The causticization process (also known as the $Gossage$ process) is an industrial method used for the production of $NaOH$ (caustic soda).
It involves heating a $10\%$ solution of sodium carbonate $(Na_2CO_3)$ with a slight excess of milk of lime $(Ca(OH)_2)$.
The chemical reaction is:
$Na_2CO_3(aq) + Ca(OH)_2(aq) \to CaCO_3(s) \downarrow + 2NaOH(aq)$

(C) When carbon monoxide $(CO)$ is passed over solid sodium hydroxide $(NaOH)$ at a temperature of $200\,^{\circ}C$ and under pressure,it undergoes a chemical reaction to form sodium formate $(HCOONa)$.
The reaction is as follows:
$NaOH + CO \xrightarrow[5-10 \ atm]{200\,^{\circ}C} HCOONa$

(A) In the Solvay process,the overall reaction is: $2NaCl + CaCO_3 \rightarrow Na_2CO_3 + CaCl_2$.
The process involves the use of $NH_3$ as a catalyst,which is recovered by reacting the byproduct $NH_4Cl$ with $Ca(OH)_2$: $2NH_4Cl + Ca(OH)_2 \rightarrow 2NH_3 + CaCl_2 + 2H_2O$.
Additionally,$CO_2$ is recovered from the thermal decomposition of limestone: $CaCO_3 \rightarrow CaO + CO_2$.
Thus,$NH_3$ and $CO_2$ are the products that are recycled back into the process.

(C) In the $Solvay$ process,the overall reaction is: $2NaCl + CaCO_3 \rightarrow Na_2CO_3 + CaCl_2$.
However,the process involves the recovery of ammonia $(NH_3)$ using lime $(Ca(OH)_2)$.
The reaction for ammonia recovery is: $2NH_4Cl + Ca(OH)_2 \rightarrow 2NH_3 + CaCl_2 + 2H_2O$.
The by-products obtained from the process are $CaCl_2$ (calcium chloride) and $NH_3$ (which is recycled).
Looking at the options provided,the question asks for useful by-products. In the context of the industrial process,$NH_4Cl$ is formed as an intermediate which is then treated with quick lime ($CaO$ or $Ca(OH)_2$) to recover $NH_3$. Thus,the combination of $NH_4Cl$ solution and quick lime is essential for the regeneration of ammonia,making them the key components in the by-product management cycle.

(C) Limestone is used as a raw material in the preparation of sodium carbonate by the Solvay process.
The Solvay process produces sodium carbonate $(Na_2CO_3)$ using brine (as a source of sodium chloride,$NaCl$) and limestone (as a source of calcium carbonate,$CaCO_3$).
The overall chemical reaction is:
$2NaCl + CaCO_3 \rightarrow Na_2CO_3 + CaCl_2$

(B) $NaOH$ is a deliquescent substance. When exposed to the atmosphere,it absorbs moisture from the air and dissolves in it to form a concentrated solution,which appears as a fluid layer around the crystals.

(A) When $Na_2CO_3$ reacts with $SO_2$ in an aqueous medium,the reaction proceeds as follows:
$Na_2CO_3 + H_2O + 2SO_2 \to 2NaHSO_3 + CO_2$
Thus,the product formed is sodium bisulphite $(NaHSO_3)$.

(B) Baking soda is used for baking purposes.
The chemical formula of baking soda is $NaHCO_3$.
Baking soda is chemically known as sodium bicarbonate or sodium hydrogen carbonate.

(C) The common name for anhydrous sodium carbonate is soda ash.
Chemical Formula: $Na_2CO_3$
$Na_2CO_3 \cdot 10H_2O$ is known as washing soda.

(C) Molten sodium is used as a coolant in nuclear reactors because it has a high thermal conductivity and a low melting point,which allows it to efficiently absorb and transfer the heat generated by nuclear fission.

(D) The preparation of $NaOH$ is done by the electrolysis of an aqueous solution of sodium chloride (brine),known as the chlor-alkali process.
The chemical reaction is: $2NaCl(aq) + 2H_2O(l) \to 2NaOH(aq) + Cl_2(g) + H_2(g)$.
At the anode,$Cl_2$ gas is released.
At the cathode,$H_2$ gas is released.
Therefore,both $Cl_2$ and $H_2$ are released.

(B) Lye is a common name for a strong alkaline solution,most commonly referring to sodium hydroxide $(NaOH)$ or potassium hydroxide $(KOH)$. It is highly caustic and is used in various industrial processes,such as soap making.

(D) $Na$ has a low ionisation potential.
When $Na$ is placed in a Bunsen flame,the heat energy is sufficient to excite the valence electron to a higher energy level.
When this electron returns to the ground state,it emits energy in the form of yellow light,which corresponds to the characteristic wavelength of $Na$.

(D) $1$. Electrolysis of an aqueous $NaCl$ solution produces $H_2$ gas at the cathode,not $Na$ metal,because $H_2O$ is reduced more easily than $Na^+$.
$2$. Elemental sodium $(Na)$ is a highly reactive metal and is easily oxidized to $Na^+$.
$3$. Elemental sodium is highly soluble in liquid ammonia,forming a deep blue solution due to the presence of ammoniated electrons.
$4$. Alkali metals,including sodium,are strong reducing agents because they have low ionization enthalpies and readily lose their valence electron.

(D) The Solvay process uses brine ($NaCl$ solution),limestone $(CaCO_3)$,ammonia $(NH_3)$,and coke $(C)$ as raw materials.
$H_2SO_4$ is not involved in the Solvay process.
Therefore,the correct option is $D$.

(A) The correct answer is $A$.
In Castner’s process,fused sodium hydroxide $(NaOH)$ is electrolysed at a temperature of $330 \ ^oC$ to extract metallic sodium $(Na)$.
The reactions are:
At cathode: $Na^+ + e^- \rightarrow Na$
At anode: $4OH^- \rightarrow 2H_2O + O_2 + 4e^-$

(A) The correct answer is $(A)$.
Excess of $Na^{+}$ ions in the human body leads to an increase in blood volume and pressure,which causes high $B.P.$ (blood pressure).

(D) When $Na$ is heated in the presence of air or oxygen,it burns to form a mixture of sodium oxide $(Na_2O)$ and sodium peroxide $(Na_2O_2)$.

(B) reducing agent is a substance that donates electrons easily.
Sodium $(Na)$ is an alkali metal with the electronic configuration $[Ne] 3s^1$.
It can easily lose its valence electron to achieve a stable noble gas configuration $([Ne])$.
Among the given options,$Na$ has the lowest ionization enthalpy and acts as the strongest reducing agent.

(B) Sea water contains a significant amount of $MgCl_2$,which is used to extract $Mg$.
The extraction of $Mg$ from sea water is commercially known as the $Dow$ sea water process.

(B) Magnesium $(Mg)$ is the central metal ion present in the porphyrin ring of chlorophyll,the green pigment in plants.
It plays a crucial role in capturing sunlight during the process of photosynthesis.

(D) . Metallic magnesium is prepared by the electrolysis of molten $MgCl_2$ (Down's process or similar electrolytic methods).
During electrolysis,the salt dissociates as follows:
$MgCl_2 \text{ (molten)} \to Mg^{2+} + 2Cl^-$
At the cathode: $Mg^{2+} + 2e^- \to Mg$ (Reduction)
At the anode: $2Cl^- \to Cl_2 + 2e^-$ (Oxidation)
Electrolysis of aqueous solutions is not used because $H_2$ gas would be evolved at the cathode instead of $Mg$ due to the higher reduction potential of water.

(D) The correct answer is $D$.
Calcium is an alkaline earth metal,which is highly reactive and cannot be obtained by carbon reduction.
It is extracted by the electrolysis of molten $CaCl_2$ (fused salt) because electrolysis of aqueous $CaCl_2$ would result in the evolution of hydrogen gas at the cathode instead of calcium metal.
At the cathode: $Ca^{+2} + 2e^{-} \to Ca$
At the anode: $2Cl^{-} \to Cl_2 + 2e^{-}$

(A) Calcium cyanamide is a chemical compound with the formula $CaCN_2$. It is produced by the reaction of calcium carbide with nitrogen at high temperatures: $CaC_2 + N_2 \rightarrow CaCN_2 + C$. It is commonly used as a fertilizer.

(C) The dark red colour of fireworks is produced by the presence of Strontium $(Sr)$ salts.
$Na$ produces a yellow colour,$Ba$ produces an apple green colour,and $K$ produces a lilac colour.

(A) The hydroxide of $K^{+}$,which is $KOH$,is a strong base and is highly soluble in water due to the high hydration energy of the $K^{+}$ ion and the lattice energy considerations.
In contrast,$Zn(OH)_2$,$Al(OH)_3$,and $Ca(OH)_2$ have significantly lower solubilities in water compared to $KOH$.

(A) The correct option is $(A)$.
Magnesium $(Mg)$ burns with an intense,brilliant white light.
Because of this property,$Mg$ wire or ribbon is used in flash bulbs for photography,as well as in fireworks and signal fires.

(B) Lime paste,also known as mortar,is a mixture of $Ca(OH)_2$ (slaked lime),sand,and water. $Ca(OH)_2$ acts as the binding agent in the mixture.

(C) Magnesium $(Mg)$ is used to prepare milk of magnesia,which is a suspension of $Mg(OH)_2$ in water and acts as an antacid to treat acidity.
When $Mg$ catches fire,it reacts with $CO_2$ to form $MgO$ and $C$ $(2Mg + CO_2 \rightarrow 2MgO + C)$,meaning $CO_2$ cannot be used to extinguish a magnesium fire.
Therefore,the metal $M$ is $Mg$.

(A) The flame test is used to identify metal ions based on the characteristic colour they impart to a flame.
$Barium$ $(Ba^{2+})$ ions impart a characteristic apple-green colour to the flame.
$Calcium$ $(Ca^{2+})$ imparts a brick-red colour,and $Strontium$ $(Sr^{2+})$ imparts a crimson-red colour.

(A) The correct answer is $(A)$.
Diagonal relationship: Elements of the $2^{nd}$ period often show a resemblance to the element of the $3^{rd}$ period placed diagonally to them.
This type of behavior is called a diagonal relationship.
$Li$ (Lithium) shows a diagonal relationship with $Mg$ (Magnesium) due to their similar ionic sizes and charge-to-size ratios.

(A) Among alkali metal carbonates,only $Li_2CO_3$ decomposes on heating because of the small size of the $Li^+$ ion,which polarizes the carbonate ion effectively.
The reaction is: $Li_2CO_3 \xrightarrow{\Delta} Li_2O + CO_2 \uparrow$
Other alkali metal carbonates like $Na_2CO_3$ are thermally stable and do not decompose under ordinary heating conditions.

(D) Most alkali metal carbonates like $Na_2CO_3$ are soluble in water.
$CaCO_3$ and $ZnCO_3$ are sparingly soluble.
$Al_2(CO_3)_3$ is considered insoluble in water because it undergoes hydrolysis to form $Al(OH)_3$ and $CO_2$ gas,making it unstable in an aqueous environment.

(A) The thermal decomposition of metal nitrates depends on the position of the metal in the electrochemical series.
Nitrates of metals like $Ag$ and $Hg$ (which are low in the electrochemical series) decompose upon strong heating to yield the metal,nitrogen dioxide $(NO_2)$,and oxygen $(O_2)$.
The reaction for silver nitrate is: $2AgNO_3(s) \xrightarrow{\Delta} 2Ag(s) + 2NO_2(g) + O_2(g)$.
Other nitrates like $Pb(NO_3)_2$,$Cu(NO_3)_2$,and $Al(NO_3)_3$ decompose to form their respective metal oxides instead of the pure metal.

(D) The solution of sodium metal in liquid $NH_3$ exhibits strong reducing properties due to the presence of solvated electrons.
The reaction is given by: $Na + (x + y)NH_3 \rightleftharpoons [Na(NH_3)_x]^+ + [e(NH_3)_y]^-$.
Here,$[e(NH_3)_y]^-$ represents the solvated electron,which is responsible for the blue color and the strong reducing nature of the solution.

(D) $A] \, Na_2CO_{3(s)} \xrightarrow{\Delta} \text{No Reaction (Stable)}$
$B] \, Ag_2CO_{3(s)} \xrightarrow{\Delta} 2Ag_{(s)} + CO_{2(g)} + \frac{1}{2}O_{2(g)}$ (Residue: $Ag$)
$C] \, CuCO_{3(s)} \xrightarrow{\Delta} CuO_{(s)} + CO_{2(g)}$ (Residue: $CuO$)
$D] \, (NH_4)_2CO_{3(s)} \xrightarrow{\Delta} 2NH_{3(g)} + H_2O_{(g)} + CO_{2(g)}$ (No solid residue)
Therefore,ammonium carbonate leaves no solid residue upon heating.

(C) The reaction between potassium superoxide $(KO_2)$ and carbon dioxide $(CO_2)$ is used in breathing apparatus to produce oxygen gas.
The balanced chemical equation is: $2KO_2 + CO_2 \to K_2CO_3 + \frac{3}{2}O_2$.
Therefore,the gas produced is $O_2$.

(B) Perchloric acid $(HClO_4)$ reacts with potassium ions $(K^+)$ to form potassium perchlorate $(KClO_4)$,which is sparingly soluble in water and appears as a white precipitate.
The reaction is: $HClO_4 + KCl \rightarrow KClO_4(s) + HCl$.

(C) The solubility of ionic compounds in water depends on the balance between lattice energy and hydration energy.
For $LiF$,the small size of both $Li^+$ and $F^-$ ions results in a very high lattice energy.
This high lattice energy is not compensated by the hydration energy,making $LiF$ insoluble in water.

(D) The correct answer is $(D)$.
In aqueous solutions,the ions are hydrated.
The extent of hydration depends on the charge density of the ion.
Smaller ions have higher charge density,which leads to a greater degree of hydration.
As the atomic size increases from $Li^{+}$ to $Rb^{+}$,the charge density decreases,and consequently,the degree of hydration decreases.

(C) The reaction of metals with dilute $HNO_3$ depends on the reactivity of the metal and the concentration of the acid.
Active metals like $Mg$ and $Mn$ react with very dilute $HNO_3$ $(1-2\%)$ to produce $H_2$ gas.
Moderately reactive metals like $Zn$,$Fe$,and $Al$ react with dilute $HNO_3$ to form $NH_4NO_3$ (ammonium nitrate).
$Pb$ (Lead) reacts with dilute $HNO_3$ to form nitric oxide $(NO)$ gas,not ammonium nitrate.
The reaction is: $3Pb + 8HNO_3 \to 3Pb(NO_3)_2 + 2NO + 4H_2O$.

(B) The correct answer is $B$.
Alkali metals are highly electropositive and form basic oxides and hydroxides.
$Na$ (Sodium) is not amphoteric; it is strongly basic in nature.
Lithium is indeed the strongest reducing agent in aqueous solution due to its high hydration energy.
$Li^{+}$ has an exceptionally small size compared to other alkali metal ions.
All alkali metals dissolve in liquid ammonia to form deep blue,conducting solutions due to the presence of ammoniated electrons.

(D) When magnesium burns in air,it reacts with both oxygen and nitrogen present in the atmosphere.
The chemical reactions are as follows:
$2Mg(s) + O_2(g) \to 2MgO(s)$
$3Mg(s) + N_2(g) \to Mg_3N_2(s)$
Therefore,the product formed is a mixture of $MgO$ and $Mg_3N_2$.

(A) $KO_2$ (potassium superoxide) is used in oxygen cylinders because it reacts with $CO_2$ to produce $O_2$ and potassium carbonate $(K_2CO_3)$.
The chemical reaction is: $4KO_2 + 2CO_2 \rightarrow 2K_2CO_3 + 3O_2$.
This process simultaneously removes $CO_2$ and replenishes $O_2$ levels.

(B) The stability of alkali metal halides is determined by their lattice energy.
Lattice energy is inversely proportional to the size of the cation.
As the size of the alkali metal cation increases down the group $(Li^+ < Na^+ < K^+ < Cs^+)$,the lattice energy decreases.
However,for alkali metal chlorides,the stability is often discussed in terms of the strength of the ionic bond,which is higher for smaller cations due to higher charge density.
Actually,the standard order of stability for alkali metal chlorides is $LiCl > NaCl > KCl > CsCl$ based on lattice energy.
Given the options provided,the question likely refers to the thermal stability or the trend of increasing ionic character/decreasing lattice energy.
Re-evaluating the provided options,option $(B)$ represents the order of increasing size of the cation,which corresponds to decreasing lattice energy.
If the question implies stability in terms of lattice energy,the correct order is $LiCl > NaCl > KCl > CsCl$.
Since this is not an option,we select the order of increasing metallic character/size which is $CsCl > KCl > NaCl > LiCl$.

(B) Reaction $(i)$ and $(ii)$ are correct as alkali metals react with water to form hydroxides and hydrogen gas.
Reaction $(iv)$ is correct as sodium nitrate decomposes to sodium nitrite and oxygen on heating.
Reaction $(iii)$ is incorrect. Lithium nitrate,unlike other alkali metal nitrates,decomposes to form lithium oxide,nitrogen dioxide,and oxygen:
$4LiNO_3 \xrightarrow{\Delta} 2Li_2O + 4NO_2 \uparrow + O_2 \uparrow$.

(D) The solubility of carbonates and bicarbonates depends on the lattice energy and hydration energy.
$CaCO_3$ is a salt of an alkaline earth metal and is practically insoluble in water.
Among the alkali metal bicarbonates,solubility increases down the group due to the decrease in lattice energy being more significant than the decrease in hydration energy.
Therefore,the solubility order is $CaCO_3 < NaHCO_3 < KHCO_3$.
Thus,the correct option is $D$.

(C) The correct answer is $(C)$.
All metal nitrates and acetates are soluble in water.