p-Block (15 and 16)

Question 1

____ is the most abundant element of Earth

Answer 1

Oxygen

Question 2

Which elements of g16 show allotropy? Which oxides are acidic?

Answer 2

all

Question 3

Amongst tetrafluorides, SF4 is a _____, SeF4 a ______ and TeF4 a _______.
These fluorides have ______ hybridisation, and thus ___________ structures

Answer 3

gas, liquid, solid

sp3d, trigonal bipyramidal (seesaw geometry)

Question 4

Dihalides (Cl, Br) hybridization? Which are dimers?

Answer 4

sp3

all (undergoes disproportionation)

Question 5

3 steps of preparation for oxygen? (decompisition)

Answer 5

Heating of oxygen-containing salts (chlorates, nitrates, permanganates), thermal decomposition of lower metal oxides, decomposition of H2O3

Question 6

Large scale prep of oxygen?

Industrial prep?

Answer 6

Electrolysis. Oxygen is released at the anode

Removing water and CO2 from air, then fractional distillation

Question 7

Ozone is at a height of ___km. Prep of ozone from oxygen gives ___% ozone

If the concentration of ozone rises above about ___ parts per million, breathing becomes uncomfortable resulting in headache and nausea

Answer 7

20
10
100

Question 8

When ozone reacts with an excess of potassium iodide solution buffered with a ___________ (pH ____), iodine is liberated which can be titrated against a standard solution of __________________. This is a
quantitative method for estimating O3 gas.

Answer 8

borate buffer, 9.2

sodium thiosulphate

Question 9

Ozone bond angle? Bond length?

Answer 9

117

128pm

Question 10

Lab synthesis of SO2?

Industrial synthesis of SO2?

Answer 10

Treating sulphite with dilute sulphuric acid

Roasting of sulphide ores

Question 11

SO2 + Cl2

Answer 11

SO2Cl2

Question 12

The sulphuric acid obtained by Contact process is _____ pure.

Answer 12

96-98%

Question 13

Order of oxidizing strength of phosphoric, nitric and sulphuric acid?

Answer 13

phosphoric acid < sulphuric acid < nitric acid

Question 14

S8 angle?

S6 angle?

Answer 14

107

102

Question 15

Which g15 elements show allotropy

Answer 15

All except nitrogen

Question 16

HNO2 disproportionate to

Answer 16

HNO3 + NO

Question 17

In g15, all trihalides except ____ is covalent

Answer 17

BiF3

Question 18

NH3 Prep?

Answer 18

1. (NH4)2CO3 decompisition

2. Ammonia salts with alkali

Question 19

Ammonia bond angle

Answer 19

107

Question 20

Cu and Zn with dilute nitric acid gives

with conc nitric acid?

Answer 20

NO, N2O (resp)

NO2

Question 21

A brown ring at the interface between the _________ and ____________ indicates the presence
of nitrate ion in solution.

Answer 21

solution, sulphuric acid layers

Question 22

What is used for pickling stainless steel?

Answer 22

HNO3

Question 23

White P in NaOH gives?

Answer 23

PH3, NaH2PO2

Question 24

alpha black phosphorus crystal structure?

Answer 24

monoclinic or rhombohedral

Question 25

Ca3P2 with H2O or dil HCl gives? How is the product purified

Answer 25

Phosphine

PH3 + HI —–> PH4I + KI ——-> KI + H2O + PH3

Question 26

PH3 explodes with trace oxidising agents like

Answer 26

HNO3, Cl2 Br2

Question 27

The solution of PH3 in water decomposes

in presence of light giving

Answer 27

red phosphorus and H2

Question 28

Finely divided metals on heating with ____ give corresponding chlorides

Answer 28

PCl5