Online Test — The s-Block Elements
20 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 20
The general valence-shell configuration of alkali metals is:
ns2
ns1
ns2np1
ns2np6
Explanation: Group 1 elements have a single outermost electron, ns1, and form +1 ions.
Question 2 of 20
Which alkali metal gives a lilac (pale violet) flame colour?
Na
Li
K
Cs
Explanation: Potassium gives a characteristic lilac flame, distinguishing it from sodium (yellow) and lithium (crimson).
Question 3 of 20
Down Group 1, the ionisation enthalpy:
increases
decreases
remains constant
first decreases then increases
Explanation: Increasing size and shielding make the valence electron easier to remove, so ionisation enthalpy decreases down the group.
Question 4 of 20
The strongest reducing agent in aqueous solution among alkali metals is:
Cs
K
Na
Li
Explanation: Lithium has the most negative E° (−3.04 V) because of its very high hydration enthalpy.
Question 5 of 20
The only alkali metal that reacts directly with nitrogen to form a nitride is:
Lithium
Sodium
Potassium
Caesium
Explanation: Lithium alone forms Li3N, an anomaly reflecting its small size and the Li–Mg diagonal relationship.
Question 6 of 20
Washing soda is:
NaHCO3
NaOH
Na2CO3·10H2O
NaCl
Explanation: Washing soda is hydrated sodium carbonate, Na2CO3·10H2O, made by the Solvay process.
Question 7 of 20
Caustic soda (NaOH) is manufactured by:
Solvay process
electrolysis of brine
heating limestone
Haber process
Explanation: NaOH is made by electrolysis of aqueous NaCl (brine), e.g. in the Castner–Kellner cell.
Question 8 of 20
The general valence configuration of alkaline earth metals is:
ns1
ns2
ns2np2
(n-1)d1ns2
Explanation: Group 2 elements have two valence electrons, ns2, and form +2 ions.
Question 9 of 20
Which oxide is amphoteric?
Na2O
MgO
BeO
BaO
Explanation: BeO (like Al2O3) is amphoteric, reacting with both acids and alkalis — part of the Be–Al diagonal relationship.
Question 10 of 20
Plaster of Paris is obtained by heating gypsum to about 393 K. Its formula is:
CaSO4·2H2O
CaSO4·½H2O
CaSO4
CaCO3
Explanation: Gypsum (CaSO4·2H2O) loses most of its water to give the hemihydrate CaSO4·½H2O, plaster of Paris.
Question 11 of 20
Quicklime is obtained by heating limestone. Quicklime is:
Ca(OH)2
CaCO3
CaO
CaSO4
Explanation: CaCO3 → CaO + CO2; the residue CaO is quicklime.
Question 12 of 20
Which of these metals gives an apple-green flame?
Ca
Sr
Ba
Mg
Explanation: Barium gives an apple-green flame; Ca is brick-red and Sr is crimson, while Mg gives no flame colour.
Question 13 of 20
Lithium shows a diagonal relationship with:
Be
Mg
Al
Ca
Explanation: Li and Mg have similar charge-to-radius ratios, so they share nitride formation and sparingly soluble carbonates.
Question 14 of 20
The metal ion at the centre of the chlorophyll molecule is:
Mg2+
Ca2+
Na+
K+
Explanation: Magnesium is the central ion of chlorophyll, essential for photosynthesis.
Question 15 of 20
The sodium–potassium pump is powered by:
sunlight
ATP
diffusion alone
osmosis
Explanation: The Na–K pump uses energy from ATP to move ions against their concentration gradients.
Question 16 of 20
Which ion is concentrated mainly inside cells?
Na+
Ca2+
K+
Cl-
Explanation: K+ is the major intracellular cation, while Na+ is concentrated outside cells.
Question 17 of 20
Why is BeCl2 largely covalent?
Be is a large atom
Be2+ has low charge density
Be2+ is very small with high polarising power
chlorine is highly polarising
Explanation: The small, highly charged Be2+ ion strongly polarises chloride (Fajans' rules), giving covalent character.
Question 18 of 20
Baking soda is:
Na2CO3
NaHCO3
NaOH
Na2O2
Explanation: Baking soda is sodium hydrogencarbonate, NaHCO3, used as an antacid and a source of CO2 in baking.
Question 19 of 20
Down Group 2, the reactivity of the metals:
decreases
increases
stays the same
is zero
Explanation: Reactivity increases down the group as ionisation enthalpy falls and electron loss becomes easier.
Question 20 of 20
Which alkali metal forms a superoxide (MO2) on burning in excess oxygen?
Li
Na
K
all of them equally
Explanation: Potassium (and Rb, Cs) form superoxides KO2; Li forms the oxide and Na the peroxide.