75 free MCQs on s-Block Elements with worked answers and explanations. Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.
Take the timed s-Block Elements chapterwise test →Below are 75 practice questions on s-Block Elements, sorted Easy → Hard. Tap “Show answer & explanation” under any question to check yourself. Want the full theory first? Read the s-Block Elements notes.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Q1.
Why are the alkali metals the most electropositive elements in their respective periods?
Answer: A. They have low ionisation enthalpies and lose the single ns<sup>1</sup> electron easily
Why: Alkali metals have the lowest ionisation enthalpies in their periods, so they readily lose the loosely held ns<sup>1</sup> electron, making them the most electropositive (strongly metallic) elements.
Q2.
On moving down Group 1 from Li to Cs, the ionisation enthalpy:
Answer: B. Decreases
Why: Down the group atomic size increases and the outer electron is more shielded and farther from the nucleus, so ionisation enthalpy decreases from Li to Cs.
Q3.
Lithium, sodium and potassium are kept under kerosene, but which alkali metals are so reactive that they are stored in sealed tubes?
Answer: C. Rubidium and caesium
Why: Rubidium and caesium react explosively even with traces of air and moisture, so they are kept in sealed glass tubes rather than merely under kerosene.
Q4.
Which property correctly distinguishes Group 2 (alkaline earth) metals from Group 1 (alkali) metals of the same period?
Answer: D. Group 2 metals are harder and have higher melting points
Why: With two bonding electrons and smaller size, Group 2 metals have stronger metallic bonding, so they are harder and melt higher than the corresponding alkali metals.
Q5.
Which alkaline earth metal and which alkali metal do NOT impart a characteristic colour to a Bunsen flame?
Answer: A. Be and Mg among Group 2; none of Group 1
Why: Beryllium and magnesium have electrons too tightly bound to be excited by a flame, so they give no colour; all the alkali metals, including Li, do impart flame colours.
Q6.
Which groups form the s-block of the periodic table?
Answer: A. Groups 1 and 2
Why: The s-block consists of Group 1 (alkali metals) and Group 2 (alkaline earth metals) whose outermost electron is in an s orbital.
Q7.
What is the common feature of alkali metals (Group 1)?
Answer: A. One valence electron (ns<sup>1</sup>)
Why: All alkali metals have one valence electron in the outermost s orbital (ns<sup>1</sup> configuration).
Q8.
Which metal is stored under kerosene oil to prevent reaction with air and moisture?
Answer: A. Sodium
Why: Sodium is highly reactive with air and water and is stored submerged in kerosene oil.
Q9.
What gas is produced when sodium reacts with water?
Answer: A. Hydrogen
Why: 2Na + 2H<sub>2</sub>O → 2NaOH + H<sub>2</sub>. The hydrogen gas evolved can ignite due to the heat produced.
Q10.
Which alkali metal is the softest metal?
Answer: A. Caesium
Why: Caesium is the softest alkali metal (and among all metals); it can be cut with a knife.
Q11.
Baking soda is the common name for:
Answer: A. NaHCO<sub>3</sub>
Why: Sodium bicarbonate (NaHCO<sub>3</sub>) is baking soda, used in baking and as an antacid.
Q12.
Washing soda is:
Answer: A. Na<sub>2</sub>CO<sub>3</sub>·10H<sub>2</sub>O
Why: Washing soda is sodium carbonate decahydrate (Na<sub>2</sub>CO<sub>3</sub>·10H<sub>2</sub>O), used in water softening and cleaning.
Q13.
Caustic soda is:
Answer: A. NaOH
Why: Sodium hydroxide (NaOH) is commonly called caustic soda; it is a strong base used in soap making.
Q14.
The Solvay process is used to manufacture:
Answer: A. Sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>)
Why: The Solvay (ammonia-soda) process produces sodium carbonate from salt, ammonia, and CO<sub>2</sub>.
Q15.
Milk of magnesia is a suspension of:
Answer: A. Mg(OH)<sub>2</sub>
Why: Milk of magnesia is a suspension of magnesium hydroxide Mg(OH)<sub>2</sub> in water, used as an antacid and laxative.
Q16.
Plaster of Paris is:
Answer: A. CaSO<sub>4</sub>·0.5H<sub>2</sub>O (hemihydrate)
Why: Plaster of Paris is calcium sulfate hemihydrate (CaSO<sub>4</sub>·0.5H<sub>2</sub>O), made by heating gypsum.
Q17.
Gypsum is:
Answer: A. CaSO<sub>4</sub>·2H<sub>2</sub>O
Why: Gypsum is calcium sulfate dihydrate (CaSO<sub>4</sub>·2H<sub>2</sub>O), a naturally occurring mineral.
Q18.
Limestone is:
Answer: A. CaCO<sub>3</sub>
Why: Limestone is calcium carbonate (CaCO<sub>3</sub>), a widely used building and industrial material.
Q19.
Quicklime is:
Answer: A. CaO
Why: Quicklime (CaO) is produced by heating limestone: CaCO<sub>3</sub> → CaO + CO<sub>2</sub> (calcination).
Q20.
Slaked lime is:
Answer: A. Ca(OH)<sub>2</sub>
Why: Slaked lime Ca(OH)<sub>2</sub> is produced when water is added to quicklime: CaO + H<sub>2</sub>O → Ca(OH)<sub>2</sub>.
Q21.
Which s-block element is essential for the human body as a bone constituent?
Answer: A. Calcium
Why: Calcium (as Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>) is the main mineral in bones and teeth, and is vital for nerve and muscle function.
Q22.
Beryllium (Be) is anomalous among Group 2 elements because it forms:
Answer: A. Covalent compounds (high charge density, small size)
Why: Be has the smallest ionic radius and highest charge density in Group 2, causing it to form covalent bonds and behave more like aluminium (diagonal relationship).
Q23.
Which alkali metal has the smallest atomic radius?
Answer: A. Lithium
Why: Lithium is the first and smallest alkali metal; atomic radius increases down the group as shells are added.
Q24.
Sodium chloride (common salt) is produced by:
Answer: A. Mining rock salt or evaporation of seawater
Why: Salt is obtained naturally from rock salt deposits or by evaporation of seawater in salt pans.
Q25.
Which of the following is a radioactive alkali metal?
Answer: A. Francium (Fr)
Why: Francium is the heaviest alkali metal and is intensely radioactive (all isotopes are radioactive, half-life <22 min).
Q26.
The solubility of alkaline earth metal hydroxides increases down the group (Be(OH)<sub>2</sub> < Mg(OH)<sub>2</sub> < ... < Ba(OH)<sub>2</sub>) mainly because:
Answer: B. Lattice enthalpy decreases faster than hydration enthalpy down the group
Why: Down the group the decrease in lattice enthalpy outweighs the decrease in hydration enthalpy, so the net energetics favour greater solubility of the heavier hydroxides.
Q27.
When lithium, sodium and potassium are heated in excess oxygen, the principal products are respectively:
Answer: C. Monoxide, peroxide and superoxide
Why: Lithium forms mainly the monoxide Li<sub>2</sub>O, sodium forms the peroxide Na<sub>2</sub>O<sub>2</sub>, and potassium (and heavier metals) form superoxides such as KO<sub>2</sub>.
Q28.
Assertion: Lithium salts are mostly hydrated while other alkali-metal salts are usually anhydrous. Reason: Li<sup>+</sup> has the largest charge-to-size ratio among alkali-metal ions.
Answer: D. Both assertion and reason are true and the reason explains the assertion
Why: The small Li<sup>+</sup> has the highest charge density, giving the strongest hydration; hence its salts such as LiCl.2H<sub>2</sub>O are hydrated, unlike the larger alkali-metal ions.
Q29.
The thermal stability of the carbonates of Group 2 follows the order BeCO<sub>3</sub> < MgCO<sub>3</sub> < CaCO<sub>3</sub> < SrCO<sub>3</sub> < BaCO<sub>3</sub> because, down the group:
Answer: A. The cation polarises the carbonate ion less, stabilising it
Why: Larger cations down the group have lower polarising power and distort the CO<sub>3</sub><sup>2-</sup> ion less, so the carbonates need higher temperatures to decompose and are thermally more stable.
Q30.
Which observation is a direct consequence of the diagonal relationship between lithium and magnesium?
Answer: B. Both form nitrides with N<sub>2</sub> and carbonates that decompose on heating
Why: Li resembles Mg: both react with N<sub>2</sub> to form nitrides, their carbonates decompose on heating, and their hydrogencarbonates do not exist as solids, reflecting the diagonal relationship.
Q31.
The anomalous behaviour of lithium compared to other alkali metals is due to:
Answer: A. Very small size and high charge density (diagonal relationship with Mg)
Why: Li is anomalously small and has a high charge density, causing it to behave more like Mg in many properties (diagonal relationship).
Q32.
Down Group 1, which property decreases?
Answer: A. First ionisation energy
Why: Down Group 1, atomic radius increases (more shells), which reduces nuclear attraction on valence electrons, lowering ionisation energy.
Q33.
Lithium forms a nitride directly with N<sub>2</sub> because:
Answer: A. Li ions are small, and Li<sub>3</sub>N has high lattice energy (similar to Mg)
Why: Li + N<sub>2</sub> → Li<sub>3</sub>N (lithium nitride); Li's small size allows formation of a stable nitride like Mg (diagonal relationship).
Q34.
The Castner-Kellner process produces NaOH and Cl<sub>2</sub> by:
Answer: A. Electrolysis of brine (NaCl solution) using mercury cell
Why: The Castner-Kellner (mercury cell) electrolyses brine to give Cl<sub>2</sub> at anode and Na amalgam at cathode; the amalgam reacts with water to give NaOH.
Q35.
Cement is mainly composed of:
Answer: A. CaO·SiO<sub>2</sub>·Al<sub>2</sub>O<sub>3</sub> (calcium aluminosilicate)
Why: Portland cement is a mixture of calcium silicates and aluminates formed by sintering limestone with clay.
Q36.
Setting of plaster of Paris involves:
Answer: A. Rehydration: CaSO<sub>4</sub>·0.5H<sub>2</sub>O + 1.5H<sub>2</sub>O → CaSO<sub>4</sub>·2H<sub>2</sub>O (gypsum)
Why: Plaster of Paris absorbs water to rehydrate back to gypsum, forming an interlocked crystalline structure that is hard.
Q37.
Which reaction represents the preparation of Na from NaCl?
Answer: A. Electrolysis of molten NaCl (Down's process)
Why: The Down's process electrolyses molten NaCl (with CaCl<sub>2</sub> to lower melting point) to obtain Na at the cathode and Cl<sub>2</sub> at the anode.
Q38.
Milk of lime is a suspension of Ca(OH)<sub>2</sub> in water. Its use in industry includes:
Answer: A. Water treatment, mortar, sugar purification
Why: Ca(OH)<sub>2</sub> (lime water / milk of lime) is used to soften water, in mortar, to neutralise acidic soil, and to purify cane sugar juice.
Q39.
Potassium superoxide (KO<sub>2</sub>) is used in:
Answer: A. Self-contained breathing apparatus (reacts with CO<sub>2</sub> and H<sub>2</sub>O to release O<sub>2</sub>)
Why: KO<sub>2</sub> + H<sub>2</sub>O → KOH + H<sub>2</sub>O<sub>2</sub> → O<sub>2</sub> released; used in breathing masks and space capsules.
Q40.
Magnesium burns in CO<sub>2</sub> because:
Answer: A. Mg reduces CO<sub>2</sub> to C (2Mg + CO<sub>2</sub> → 2MgO + C), so CO<sub>2</sub> extinguishers fail on Mg fires
Why: Magnesium is a stronger reducing agent than carbon and burns even in CO<sub>2</sub>, which is why CO<sub>2</sub> fire extinguishers cannot be used on Mg fires.
Q41.
The Solvay process steps include: salt + ammonia + CO<sub>2</sub> → NaHCO<sub>3</sub> (precipitate) → heating → Na<sub>2</sub>CO<sub>3</sub>. The ammonia is:
Answer: A. Recovered and recycled by treating NH<sub>4</sub>Cl with Ca(OH)<sub>2</sub>
Why: NH<sub>4</sub>Cl produced is treated with Ca(OH)<sub>2</sub> (slaked lime) to recover ammonia: 2NH<sub>4</sub>Cl + Ca(OH)<sub>2</sub> → CaCl<sub>2</sub> + 2NH<sub>3</sub> + 2H<sub>2</sub>O.
Q42.
Which alkaline earth metal is used in making strong lightweight alloys for aircraft?
Answer: A. Magnesium (Mg)
Why: Magnesium is very light (density 1.74 g/cm<sup>3</sup>) and is alloyed with aluminium to make lightweight, strong alloys for aerospace.
Q43.
Thermal stability of Group 2 carbonates:
Answer: A. Increases down the group (larger cations have lower charge density, stabilise CO<sub>3</sub><sup>2-</sup> more)
Why: Larger alkaline earth cations (Ca, Sr, Ba) have lower polarising power and stabilise the CO<sub>3</sub><sup>2-</sup> lattice better; BaCO<sub>3</sub> decomposes at the highest temperature.
Q44.
Hard water deposit (scale) in boilers is removed using:
Answer: A. Calgon (sodium hexametaphosphate) or HCl treatment
Why: Boiler scale (mainly CaSO<sub>4</sub> and CaCO<sub>3</sub>) can be dissolved using hydrochloric acid or prevented by sequestering agents like Calgon.
Q45.
Chlorophyll (the green plant pigment) contains which metal from the s-block?
Answer: A. Magnesium (Mg<sup>2+</sup> at the porphyrin centre)
Why: Chlorophyll has a porphyrin ring with Mg<sup>2+</sup> at its centre, essential for light absorption in photosynthesis.
Q46.
Epsom salt is:
Answer: A. MgSO<sub>4</sub>·7H<sub>2</sub>O
Why: Epsom salt is magnesium sulfate heptahydrate (MgSO<sub>4</sub>·7H<sub>2</sub>O), used as a laxative and in bath salts.
Q47.
The flame colours of alkali metals are caused by:
Answer: A. Electrons jumping from excited states back to ground state emitting visible light
Why: When atoms absorb flame energy, outer electrons are excited; on returning to ground state they emit characteristic spectral lines.
Q48.
Barium sulfate (BaSO<sub>4</sub>) is used as an X-ray contrast agent for the digestive tract because:
Answer: A. It is insoluble and non-toxic, opaque to X-rays
Why: BaSO<sub>4</sub> (barium meal) is insoluble in water and stomach acid, non-absorbable and safe; it scatters X-rays to show GI tract shape.
Q49.
Radium (Ra) was discovered by:
Answer: A. Marie and Pierre Curie
Why: Marie and Pierre Curie discovered radium (and polonium) in 1898 from pitchblende ore.
Q50.
Beryllium cannot be obtained by electrolysis of aqueous BeCl<sub>2</sub> solution because:
Answer: A. Be is above H in activity series; H<sub>2</sub> is discharged preferentially at the cathode
Why: Be<sup>2+</sup> has very high hydration enthalpy and is reduced above the reduction potential of water, so H<sub>2</sub> is released instead at the cathode in aqueous solution.
Q51.
Although Li has the most negative standard electrode potential (E° = -3.04 V), it reacts with water less vigorously than sodium. The reason is that:
Answer: C. High hydration energy makes E° very negative, but a high melting point slows the reaction
Why: The very negative E° of Li is due to its exceptionally high hydration enthalpy (a thermodynamic quantity). Kinetically, Li's high melting point keeps it solid and its small size slows the reaction, so it reacts more gently than Na.
Q52.
In the Solvay (ammonia-soda) process, which statement correctly explains why it cannot be used to manufacture potassium carbonate?
Answer: D. Potassium hydrogencarbonate (KHCO<sub>3</sub>) is too soluble to precipitate out
Why: The process relies on the low solubility of NaHCO<sub>3</sub> so it precipitates; KHCO<sub>3</sub> is appreciably soluble and does not precipitate, so K<sub>2</sub>CO<sub>3</sub> cannot be made this way.
Q53.
Beryllium chloride is a covalent compound that is polymeric in the solid state. In the solid polymer, each beryllium atom is:
Answer: A. Tetrahedrally four-coordinate through chloride bridges
Why: Solid BeCl<sub>2</sub> forms chain polymers in which each Be is bonded to four chlorines (two terminal, two bridging), giving tetrahedral four-coordination; the monomer is linear only in the vapour.
Q54.
A blue solution of sodium in liquid ammonia conducts electricity and is strongly reducing. On standing, the blue colour fades and the conductivity changes because:
Answer: B. Ammoniated electrons slowly convert to sodium amide with evolution of dihydrogen
Why: The blue colour and conductivity arise from ammoniated electrons. On standing these react: Na + NH<sub>3</sub> → NaNH<sub>2</sub> + ½H<sub>2</sub>, so the colour fades as amide forms and H<sub>2</sub> is released.
Q55.
Lithium iodide is the most covalent of the lithium halides. According to Fajans' rules this is because, compared with the other halides:
Answer: C. The iodide ion is large and most easily polarised by the small Li<sup>+</sup>
Why: The large, highly polarisable I<sup>-</sup> ion is distorted most by the small high-charge-density Li<sup>+</sup>, giving the greatest covalent character among LiF, LiCl, LiBr and LiI.
Q56.
The lattice energy of NaF is higher than NaCl because:
Answer: A. F- is smaller than Cl-, so Na-F distance is shorter and lattice energy (alpha 1/r) is higher
Why: Lattice energy ∝ (q+×q-)/(r+ + r-). F- is smaller than Cl-, decreasing internuclear distance and increasing lattice energy.
Q57.
Why does LiF have lower solubility in water than LiCl?
Answer: A. LiF has very high lattice energy; the hydration enthalpy does not overcome it
Why: LiF: high lattice energy (due to small F-) outweighs hydration energy, so it is sparingly soluble. LiCl has lower lattice energy and dissolves readily.
Q58.
Why does Na react vigorously with water while Li reacts less vigorously?
Answer: A. Na has lower first ionisation energy than Li, making it easier to ionise; also Na reacts exothermically faster
Why: Li's very high charge density means the Li+ ion is heavily hydrated, releasing more energy overall, but kinetically Li's reaction is slower due to its higher ionisation energy and the coherent film of LiOH.
Q59.
In the Down's process, CaCl<sub>2</sub> is added to NaCl to:
Answer: A. Lower the melting point from 800°C to ~600°C making electrolysis practical
Why: Pure NaCl melts at 800°C; adding CaCl<sub>2</sub> lowers the melting point (~600°C), reducing energy consumption and preventing Na vaporisation.
Q60.
Organolithium compounds (RLi) are more reactive than Grignard reagents (RMgX) because:
Answer: A. C-Li bonds are more covalent and have more ionic character; Li is more electropositive than Mg
Why: RLi has more polarised C-Li bond (Li more electropositive than Mg, less electronegative), making the carbanion character stronger and RLi more nucleophilic/basic.
Q61.
The hardness order of Group 2 metals is:
Answer: A. Be > Mg > Ca > Sr > Ba (decreases down the group as metallic bonding weakens)
Why: Down Group 2, metal-metal bonds weaken (fewer valence electrons relative to increasing atomic size), reducing hardness.
Q62.
Which Group 1 element has an anomalously high melting point compared to trend?
Answer: A. Lithium (180°C vs Na 98°C, K 63°C, Rb 39°C, Cs 28°C)
Why: Li melts at 180°C; all other alkali metals melt below 100°C. Li's small size means stronger metallic bonding (higher electron density).
Q63.
Diagonal relationship between Li and Mg: which specific property is shared?
Answer: A. Both form nitrides (Li<sub>3</sub>N and Mg<sub>3</sub>N<sub>2</sub>), have similar solubility trends, and form covalent organometallic compounds
Why: Li resembles Mg: both form nitrides directly, both LiF and MgF<sub>2</sub> are sparingly soluble, both LiOH and Mg(OH)<sub>2</sub> are weak bases, and Li<sub>2</sub>CO<sub>3</sub>/MgCO<sub>3</sub> decompose on heating.
Q64.
The pH of a 0.1 M NaOH solution is:
Answer: A. 13
Why: NaOH is a strong base. [OH-] = 0.1 M, pOH = 1, pH = 14 - 1 = 13.
Q65.
When excess Na<sub>2</sub>O<sub>2</sub> reacts with water, the products are:
Answer: A. NaOH and H<sub>2</sub>O<sub>2</sub> (2Na<sub>2</sub>O<sub>2</sub> + 2H<sub>2</sub>O → 4NaOH + O<sub>2</sub>)
Why: Na<sub>2</sub>O<sub>2</sub> (sodium peroxide) reacts with water: 2Na<sub>2</sub>O<sub>2</sub> + 2H<sub>2</sub>O → 4NaOH + O<sub>2</sub>. It is used in submarines as an O<sub>2</sub> source.
Q66.
Calcium carbide (CaC<sub>2</sub>) reacts with water to give:
Answer: A. Acetylene (C<sub>2</sub>H<sub>2</sub>) and Ca(OH)<sub>2</sub>
Why: CaC<sub>2</sub> + 2H<sub>2</sub>O → Ca(OH)<sub>2</sub> + C<sub>2</sub>H<sub>2</sub>. This reaction was historically used to generate acetylene for lamps (carbide lamps).
Q67.
Liquid ammonia is used as a solvent in which Group 1 reactions?
Answer: A. Dissolution of alkali metals in liquid NH<sub>3</sub> to give blue solutions (solvated electrons)
Why: Alkali metals dissolve in liquid NH<sub>3</sub>: Na → Na+ + e-(solvated), giving blue paramagnetic solutions. At higher concentrations they turn bronze (metallic) and conduct electricity.
Q68.
The blue colour of alkali metal solutions in liquid ammonia is due to:
Answer: A. Solvated electrons (e-(am)) absorbing light in the visible range
Why: Solvated electrons (free electrons surrounded by NH<sub>3</sub> molecules) absorb light broadly; dilute solutions are blue, concentrated solutions are metallic bronze.
Q69.
In which reaction is barium peroxide (BaO<sub>2</sub>) an important intermediate?
Answer: A. Historical preparation of H<sub>2</sub>O<sub>2</sub>: BaO<sub>2</sub> + H<sub>2</sub>SO<sub>4</sub> → BaSO<sub>4</sub> + H<sub>2</sub>O<sub>2</sub>
Why: Before modern methods, H<sub>2</sub>O<sub>2</sub> was made by treating BaO<sub>2</sub> with cold dilute H<sub>2</sub>SO<sub>4</sub>, giving insoluble BaSO<sub>4</sub> precipitate and H<sub>2</sub>O<sub>2</sub> solution.
Q70.
The standard electrode potential E° of Li/Li+ (-3.05 V) is more negative than Na/Na+ (-2.71 V). In terms of reactivity in water, however:
Answer: A. Na reacts more vigorously with water than Li, despite Li's more negative E°, due to kinetic factors
Why: Li's high hydration enthalpy means thermodynamics favours Li strongly, but a thin film of LiOH coats Li and slows the reaction kinetically; Na's film is more reactive/less coherent.
Q71.
Beryllium forms BeF<sub>2</sub> with a structure resembling:
Answer: A. SiO<sub>2</sub> (polymeric tetrahedral network via bridging F atoms in solid state)
Why: In the solid state, BeF<sub>2</sub> has a polymeric structure analogous to SiO<sub>2</sub> with bridging fluorides, reflecting Be's tendency to expand its coordination sphere (covalent character).
Q72.
Why is BeSO<sub>4</sub> more soluble in water than BaSO<sub>4</sub>?
Answer: A. Be<sup>2+</sup> has high charge density and large hydration enthalpy that overcomes the lattice energy; Ba<sup>2+</sup> is large with lower hydration enthalpy
Why: For Group 2 sulfates: solubility decreases down the group (Be > Mg > Ca > Sr > Ba) because hydration enthalpy decreases faster than lattice energy as cation size increases.
Q73.
The Solvay process cannot economically produce potassium carbonate (K<sub>2</sub>CO<sub>3</sub>) because:
Answer: A. KHCO<sub>3</sub> is too soluble in the brine solution to precipitate out as NaHCO<sub>3</sub> does
Why: The Solvay process works because NaHCO<sub>3</sub> is sparingly soluble and precipitates; KHCO<sub>3</sub> is more soluble and stays in solution, making K<sub>2</sub>CO<sub>3</sub> production by this route uneconomical.
Q74.
Sodium amalgam (Na/Hg) is used as a reducing agent. The amalgam forms because:
Answer: A. Na dissolves in mercury forming a liquid alloy (amalgam) that is safer and less reactive than pure Na
Why: Amalgams are alloys of mercury; Na dissolves in Hg, diluting its reactivity while retaining reducing power, making it safer to handle.
Q75.
Why does group 2 hydroxides become more basic and more soluble down the group?
Answer: A. Increasing cation size reduces lattice energy and increases hydration enthalpy advantage; larger M<sup>2+</sup> also holds OH- less tightly
Why: From Mg(OH)<sub>2</sub> (sparingly soluble, weakly basic) to Ba(OH)<sub>2</sub> (soluble, strongly basic): larger, less polarising cations release OH- more freely and their hydroxides have lower lattice energies.