Chemistry : The p-Block Elements

When formic acid is heated with conc. H₂SO₄  the gas evolved is

• Only CO₂

• Only CO₂

• mixture of CO and CO₂

• a mixture of SO₂ and CO₂

excess of PCl₅ reacts with concentrated H₂SO₄ giving

• chlorosulphuric acid

• sulphurous acid

• sulphury chloride

• thionyl chloride

The statement that is not correct is

• Hypophosphorous acid reduces silver nitrate to silver

• In solid state PCl₅ exists as [PCl₄]⁺ [PCl₆]^-

• Pure phosphine is non-inflammable

• Phosphorous acid on heating disproportionates to give metaphosphonic acid and phosphine

On heating with concentrated NaOH solution in an inert atmosphere of CO₂ white phosphorus gives a gas. Which of the following statement is incorrect about the gas?

• It is less basic than NH₃

• It is more basic than NH₃

• It is highly poisonous and has smell like rotten fish

• Its solution in water decomposes in the presence of light

${\mathrm{MSO}}_4 \stackrel{{\mathrm{NH}}_4\mathrm{OH}}{\to }\underset{\mathrm{White}}{\downarrow \mathrm{X}} \underset{\mathrm{Excess}}{\overset{{\mathrm{NH}}_4\mathrm{OH}}{\to }} \mathrm{Y}\stackrel{{\mathrm{H}}_2\mathrm{S}}{\to } \downarrow \mathrm{Z}$.Here, M and Z are

• Cu, ZnS

• Zn, ZnS

• Fe, FeS

• Al, Al₂S₃

How many ions per molecule are produced in the solution, when Mohr salt is dissolved in excess of water?

• 4

• 5

• 6

• 10

The salt which responds to dilute and concentrated H₂SO₄ is

• CaF₂

• Ba(NO₃)₂

• Na₂SO₄

• Na₃PO₄

The aqueous solution of following salt will have the lowest pH

• NaClO₃

• NaClO

• NaClO₂

• NaClO₄

For one of the element various successive ionisation enthalpies (in kJ mol^-1) are given below.

	1st	2nd	3rd	4th	5th
IE	5775	1810	2750	11,580	14820

The element is

• Si

• P

• Al

• Mg

The property which is not true about fluorine is

• most of its reactions are exothermic

• it forms only one oxo acid

• highest electronegativity

• high F-Fbond dissociation enthalpy