Periodic table

Question 1

Period 3 Electronegativity trend

Answer 1

Across the period, NC increases, SE remains relatively constant since electrons are added to the same shell-> ENC increases
Therefore stronger electrostatic forces of attraction between the nucleus and the electron pair in a covalent bond, electronegativity increases.

Question 2

Electrical conductivity and structure of Na, Mg and Al

Answer 2

Giant metallic lattice structure

High electrical conductivity:
presence of sea of delocalized electrons as mobile charge carriers to conduct electricity.

Question 3

Electrical conductivity and structure of Si

Answer 3

Giant molecular

Low electrical conductivity as Si is a metaloid

Question 4

Electrical conductivity and structure of P, S, Cl, Ar

Answer 4

Simple molecular structure

Non-conductors of electricity in any state
-electrons are localized in covalent bonds and there are no mobile electrons to conduct electricity

Question 5

Na2O with water

Answer 5

Dissolves completely in water

Na2O + H2O -> 2NaOH pH 14

Question 6

MgO with water

Answer 6

Dissolves partially due to high LE of MgO

MgO + H2O -> Mg(OH)2 pH 9

Question 7

Al2O3 with water

Answer 7

does not dissolved bc of high LE pH 7

Question 8

SiO2 with water

Answer 8

no reaction bc of strong covalent bonds pH 7

Question 9

P4O10 with water

Answer 9

dissolves in water

P4O10 + H2O -> H3PO4 pH 2

Question 10

SO3 with water

Answer 10

dissolved in water

SO3 + H2O -> H2SO4 pH 2

Question 11

Al(OH)3 with acid

Answer 11

Forms salt and water

Al(OH)3 + 3H+ -> Al3+ +3H2O

Question 12

Al(OH)3 with base

Answer 12

Dissolves in excess to form colourless complex

Al(OH)3 + OH- -> Al(OH)4-

Question 13

Na2O/MgO with base

Answer 13

No reaction

Question 14

Na2O/MgO with acid

Answer 14

Form salt and water

Question 15

AlO3 with acid

Answer 15

Forms salt and water
AlO3 + 6HCl -> 2AlCl3 + 3H2O

Question 16

AlO3 with base

Answer 16

Dissolves in excess to form colourless complex

Al2O3 + 2NaOH + 3H2O -> 2NaAl(OH)4

Question 17

SiO2, P4O10, SO3 with acid

Answer 17

No reaction

Question 18

SiO2 with base

Answer 18

Reacts with hot concentrated NaOH

SiO2 + NaOH -> Na2SiO3 + H2O

Question 19

P4O10 with base

Answer 19

P4O10 + 12NaOH -> 4Na3PO4 + 6H2O

Question 20

SO3 with base

Answer 20

SO3 + 2NaOH -> Na2SO4 + H2O

Question 21

NaCl with water

Answer 21

undergoes hydration, not hydrolysis

Question 22

MgCl2, AlCl3 with water

Answer 22

Undergoes hydration , undergoes slight hydrolysis

Question 23

SiCl4, PCl5 with water

Answer 23

Does not undergo hydration, undergoes complete hydrolysis (atoms have vacant and energetically available 3d orbitals to accept the lone pair from H2O, forming a dative bond.

Question 24

Why does CCl4 not hydrolyse in water

Answer 24

C has no energetically accessible d-orbitals for dative bonding with H2O molecules

Question 25

Difference between hydration and hydrolysis

Answer 25

hydration- formation of ion-dipole interactions hydrolysis- chemical reaction

Question 26

Observations of NaCl in water

Answer 26

dissolves completely pH 7

Question 27

Observations of MgCl2 in water

Answer 27

dissolved completely pH 6.5

Question 28

Observations of AlCl3 in water

Answer 28

dissolves completely in excess forms white solid with white fumes of HCl in limited amount of water pH 3

Question 29

Observations of SiCl4 in water

Answer 29

Reacts violently with water, evolving heat and white fumes of HCl pH2

Question 30

Observations of PCl5 in water

Answer 30

Dissolves completely in excess, reacts violently in limited amount of water, evolving heat and white fumes of HCL pH 2

Question 31

Explain the trend of thermal stability of Group 2 metal carbonates down the group

Answer 31

Down the group, IR of cations increases, charge density decreases-> polarizing power decreases, electron cloud less distorted. C-O bond weakened to smaller extent, energy needed to break the C-O bond increases, ease of decomposition decreases.

Question 32

Group 17 Electronegativity trend

Answer 32

Down the group, AR increase, electrostat att decrease, tendency to attract electrons decreases, electronegativity decreases

Question 33

Explain the trend of volatility down Group 17 elements

Answer 33

Down the group, size of electron cloud increases, more easily polarized, strength of idid attractions increase, more energy needed to overcome, boiling point increases down the group, volatility decreases.

Question 34

Explain the trend of Group 17 halogens as oxidizing agents

Answer 34

Down the group, AR increases, attraction decreases, tendency to gain electron decreases, strength as OA decreases

Question 35

Trend of thermal stability for Group 17

Answer 35

From Cl to I, AR increases, effectiveness of orbital overlap decreases, bond strength decreases, energy needed to break the bond decreases, thermal stability decreases