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The s-Block Elements

Multiple Choice Questions

301.

The molecular formula of bleaching powder is

CaCl₂
Ca₂OCl₂
CaOCl₂
CaCl₂.CaOCl

302.

A solution of sodium metal in liquid ammonia is a strong reducing agent due to the presence of

sodium atoms
sodium hydride
sodium amide
solvated electron

303.

Which of the following metals has highest melting point

Barium
Calcium
Strontium
Radium

304.

Which of the following pairs of compounds cannot exist together?

NaHCO₃ and NaCl
NaHCO₃ and NaOH
NaHCO₃ and Na₂CO₃
Na₂CO₃and NaOH

305.

Which of the following properties of lithium does not show diagonal relationship with magnesium?

Formation of Li⁺ ion
Formation of Li₃N
Solubility of LiHCO₃
Thermal decomposition of Li₂CO₃

306.

Which of the following carbonates decomposes at lowest temperature?

MgCO₃
CaCO₃
BaCO₃
SrCO₃

307.
A white-coloured inorganic compound, on heating, gives a gas which turns lime water milky and residue is left which is yellow when hot and turns white on cooling. The compound is

Pb(NO₃)₂

PbCO₃

BaCO₃

ZnCO₃

ZnCO₃

Since the obtained gas turns lime water milky, it must be CO₂ and the anion present in the compound must be CO $_{3}^{2 -}$ .

The residue left after the liberation of CO₂ is yellow when hot and turns white on cooling, so it is of ZnO and the cation present in the compound is Zn²⁺. Hence, the white coloured inorganic compound is

${Zn}^{+} + {CO}_{3}^{2 -} \to {ZnCO}_{3} and the reactions are as follows : {ZnCO}_{3} \overset{∆}{\to} ZnO + {CO}_{2} {CO}_{2} + \underset{lime water}{Ca (OH)_{2}} \to \underset{calcium carbonate (milky)}{{CaCO}_{3}} + H_{2} O$