Chemistry

The p-Block Elements.

Question:

On reaction with Cl2, phosphorus forms two types of halides ‘A' and ‘B'. Halide A is yellowish-white powder but halide B' is colourless oily liquid. Identify A and B and write the formulas of their hydrolysis products.

Answer:

When dry chlorine is passed over white phosphorus heated gently in a retort, first phosphorus trichloride is formed. PCl3 further reacts with Cl2 and forms phosphorus pentachloride PCl5.
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The p-Block Elements.

Q 1.

 Why are pentahalides more covalent than trihalidcs?

Q 2.

Give the resonating structures of N02 and N2O5.

Q 3.

 With which neutral molecule is ClO isoelectronic? Is this molecule Lewis acid or base ? (Pb. Board 2009)

Q 4.

Write a balanced equation for the hydrolytic reaction of PC is in heavy water.

Q 5.

Which of the following acid forms three series of salts?
(a) H2PO2  (b) H3BO3 (C)H3PO4(d)H3PO3

Q 6.

 Why does nitrogen show catenation properties less than phosphorus ? (C.B.S.E. Foreign 2009)

Q 7.

Write two uses of ClO2

Q 8.

On heating ammonium dichromate and barium azide separately we get
(a) N2 in both cases
(b) N2 with ammonium dichromate and NO with barium azide
(c) N2O  with ammonium dichromate and N2 with barium azide
(d) N2O with ammonium dichromate and N2O with barium azide

Q 9.

Which of the following statements are correct?
(a) Among halogens, radius ratio between iodine and fluorine is maximum.
(b) Leaving F – F bond, all halogens have weaker X – X bond than X – X’ bond in interhalogens.
(c) Among interhalogen compounds maximum number of atoms ate present in iodine fluoride.
(d) Interhalogen compounds are more reactive than halogen compounds.

Q 10.

Phosphorus forms a number of oxoacids. Out of these oxoacids phosphinic acid has strong reducing property. Write its structure and also write a reaction showing its reducing behaviour.

Q 11.

 Why is N2 less reactive at room temperature?

Q 12.

Mention the conditions required to maximise the yield of ammonia.

Q 13.

 Write the order of thermal stability of the – hydrides of Group 16 elements.

Q 14.

Why is H2O a liquid and H2S a gas?

Q 15.

How is ammonia manufactured industrially?

Q 16.

 Why does R3P=0 exist but R3N=0 does not (R is an alkyl group) ?

Q 17.

Give the disproportionation reaction of H3 P03.

Q 18.

 Write two uses of ClO2

Q 19.

Why is N2 less reactive at room temperature?

Q 20.

What is the basicity of H3PO4?

Q 21.

Discuss the trends in chemical reactivity of group 15 elements.

Q 22.

Why does nitrogen show catenation properties less than phosphorus?

Q 23.

Nitric acid forms an oxide of nitrogen on reaction with P4O10. Write the reaction involved. Also write the resonating structures of the oxide of nitrogen formed.

Q 24.

Assertion (A): HI cannot be prepared by the reaction of KI with concentrated H2SO4.
Reason (R): HI has lowest H – X bond strength among halogen acids.

Q 25.

 Why is BiH3 the strongest reducing agent amongst all the hydrides of group 15 elements? (C.B.S.E. 2013)

Q 26.

How is O3 estimated quantitatively?

Q 27.

What happens when sulp’hur dioxide is passed through an aqueous solution of Fe(III) salt?

Q 28.

Comment on the nature of two S-O bonds formed in S02 molecule. Are the two S-O bonds in this molecule equal ?

Q 29.

Name two poisonous gases which can be prepared from chlorine gas

Q 30.

Explain why fluorine forms only one oxoacid, HOF.

Q 31.

 Write balanced equations for the following:
(i) NaCl is heated witlrsulphuric acid in the presence of MnO2
(ii) Chlorine gas is passed into a solution of Nal in water.

Q 32.

What is the covalence of nitrogen in N2O5 ?

Q 33.

How is nitrogen prepared in the laboratory? Write the chemical equations of the reactions . involved.

Q 34.

Illustrate how copper metal can give different products on reaction with HN03.

Q 35.

How is SO2 an air pollutant?

Q 36.

How are xenon fluorides XeF2, XeF4 and XeF6  obtained?

Q 37.

Which of the following statements are correct?
(a) All three N – O bond lengths in HNO3 are equal.
(b) All P – Cl bond lengths in PCl5 molecule in gaseous state are equal.
(c) P4  molecule in white phosphorus have angular strain therefore white phosphorus is very reactive.
(d) PCl5 is ionic in solid state in which cation is tetrahedral and anion is octahedral.

Q 38.

Write a balanced chemical equation, for the reaction showing catalytic oxidation of NH3 by atmospheric oxygen.

Q 39.

Explain why does the stability of oxoacids of chlorine increase in the order given below:
HClO < HClO2 < HClO3 < HClO4

Q 40.

P4O6 reacts with water according to equation P4O6 + 6H2O Calculate the volume of 0.1 M NaOH solution required to neutralize the acid formed by dissolving 1.1 g of P4O6 in H2O.

Q 41.

Match the items of Column I and Column II and mark the correct option.
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Q 42.

Assertion (A): HNO3 makes from passive.
Reason (R): HNO3 forms a protective layer of ferric nitrate on the surface of iron.

Q 43.

Assertion (A): SF6 cannot be hydrolysed but SF4 can be.
Reason (R): Six F atoms in SF6 prevent the attack of H2O on sulphur atom of SF6.

Q 44.

How does ammonia react with a solution of Cu2+?

Q 45.

 What happens when H3PO4 is heated?

Q 46.

Discuss the trends in chemical reactivity of group 15 elements.

Q 47.

Why does NH3 form hydrogen bond but PH3 does not?

Q 48.

 Knowing the electron gain enthalpy values of O—>O and O—>O2- as -141 and 702 kJ mol-1 respectively, how can you account for the formation of a large number of oxides having O2- species and not O?

Q 49.

Explain why inspite of nearly the same electronegativity, nitrogen forms hydrogen bonding while chlorine does not.

Q 50.

 How are XeOand XeOF4prepared?