Inorganic Chemistry

Question 1

Trend in atomic radius across Period 3

Answer 1

Decreases due to increasing nuclear charge.

Question 2

Trend in ionic radius across Period 3

Answer 2

Cations decrease, anions increase.

Question 3

Trend in melting points across Period 3

Answer 3

Increases to Si, then decreases.

Question 4

Trend in electrical conductivity across Period 3

Answer 4

Metals conduct, Si is a semiconductor, nonmetals do not conduct.

Question 5

Acid/base behavior of Na2O

Answer 5

Basic

Question 6

Acid/base behavior of MgO

Answer 6

Basic

Question 7

Acid/base behavior of Al2O3

Answer 7

Amphoteric

Question 8

Acid/base behavior of P4O10

Answer 8

Acidic

Question 9

Acid/base behavior of SO2, SO3

Answer 9

Acidic

Question 10

Reaction of NaCl with H2O

Answer 10

Dissolves, pH ≈ 7

Question 11

Reaction of MgCl2 with H2O

Answer 11

Dissolves slightly, pH ≈ 6.5

Question 12

Reaction of AlCl3 with H2O

Answer 12

Hydrolyzes, pH ≈ 3-4

Question 13

Reaction of SiCl4 with H2O

Answer 13

SiCl4 + 4H2O → Si(OH)4 + 4HCl (pH ≈ 2)

Question 14

Reaction of PCl5 with H2O

Answer 14

PCl5 + 4H2O → H3PO4 + 5HCl (pH ≈ 1-2)

Question 15

Bonding in Period 3 oxides

Answer 15

Ionic (Na2O, MgO, Al2O3), covalent (SiO2, P4O10, SO2, SO3).

Question 16

Bonding in Period 3 chlorides

Answer 16

Ionic (NaCl, MgCl2), covalent (AlCl3, SiCl4, PCl5).

Question 17

Reaction of Group 2 metals with oxygen

Answer 17

2M + O2 → 2MO

Question 18

Reaction of Group 2 metals with water

Answer 18

M + 2H2O → M(OH)2 + H2 (Mg reacts slowly, Ba reacts vigorously)

Question 19

Reaction of Group 2 metals with HCl

Answer 19

M + 2HCl → MCl2 + H2

Question 20

Reaction of Group 2 metals with H2SO4

Answer 20

M + H2SO4 → MSO4 + H2 (BaSO4 is insoluble, limiting reaction)

Question 21

Reaction of Group 2 oxides with water

Answer 21

MO + H2O → M(OH)2 (alkaline solution)

Question 22

Reaction of Group 2 oxides with acids

Answer 22

MO + 2HCl → MCl2 + H2O

Question 23

Reaction of Group 2 hydroxides with acids

Answer 23

M(OH)2 + 2HCl → MCl2 + 2H2O

Question 24

Reaction of Group 2 carbonates with acids

Answer 24

MCO3 + 2HCl → MCl2 + CO2 + H2O

Question 25

Thermal decomposition of Group 2 nitrates

Answer 25

Thermal stability increases down group (Mg easier to decompose than Ba)

Question 26

Thermal decomposition of Group 2 carbonates

Answer 26

MCO3 → MO + CO2 (stability increases down group)

Question 27

Solubility trend of Group 2 hydroxides

Answer 27

Increases down the group

Question 28

Solubility trend of Group 2 sulfates

Answer 28

Decreases down the group

Question 29

Colour of chlorine

Answer 29

Pale green gas

Question 30

Colour of bromine

Answer 30

Red-brown liquid

Question 31

Colour of iodine

Answer 31

Dark grey solid (purple vapour)

Question 32

Trend in volatility of Group 17 elements

Answer 32

Decreases down the group

Question 33

Trend in bond strength of X2 molecules

Answer 33

Decreases down the group

Question 34

Explanation of Group 17 volatility trend

Answer 34

Volatility **decreases down group** because larger atoms have stronger van der Waals forces making it harder for molecules to escape into the gas phase

Question 35

Oxidizing power of halogens

Answer 35

Decreases down the group (Cl2 > Br2 > I2)

Question 36

Reaction of halogens with hydrogen

Answer 36

H2 + X2 → 2HX (reactivity decreases down group)

Question 37

Trend in thermal stability of hydrogen halides

Answer 37

Decreases down the group (HCl > HBr > HI)

Question 38

Reactivity of halide ions as reducing agents

Answer 38

Increases down the group (I− > Br− > Cl−)

Question 39

Reaction of halide ions with AgNO3

Answer 39

Cl− → white ppt, Br− → cream ppt, I− → yellow ppt

Question 40

Solubility of AgX in NH3

Answer 40

AgCl dissolves, AgBr partially dissolves, AgI insoluble

Question 41

Reaction of halide ions with H2SO4 (Cl−)

Answer 41

NaCl + H2SO4 → NaHSO4 + HCl (misty fumes)

Question 42

Reaction of halide ions with H2SO4 (Br−)

Answer 42

NaBr + H2SO4 → NaHSO4 + HBr, then Br2 + SO2 + H2O

Question 43

Reaction of halide ions with H2SO4 (I−)

Answer 43

NaI + H2SO4 → NaHSO4 + HI, then I2 + H2S + H2O

Question 44

Reaction of Cl2 with cold NaOH

Answer 44

Cl2 + 2NaOH → NaCl + NaOCl + H2O

Question 45

Reaction of Cl2 with hot NaOH

Answer 45

3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O

Question 46

Use of chlorine in water purification

Answer 46

Cl2 + H2O → HCl + HOCl (HOCl kills bacteria)

Question 47

Why is nitrogen unreactive?

Answer 47

Strong N≡N triple bond, non-polar molecule

Question 48

Basicity of ammonia (Brønsted–Lowry theory)

Answer 48

NH3 acts as a proton acceptor (NH3 + H+ → NH4+)

Question 49

Structure and formation of NH4+

Answer 49

Tetrahedral shape, formed by NH3 + H+ → NH4+

Question 50

Reaction of ammonium salts with bases

Answer 50

NH4+ + OH− → NH3 + H2O

Question 51

Sources of nitrogen oxides (NO, NO2)

Answer 51

Lightning, combustion, vehicle exhausts

Question 52

Removal of NOx from exhaust gases

Answer 52

2CO + 2NO → N2 + 2CO2 (catalytic converter)

Question 53

Formation of PAN in photochemical smog

Answer 53

NOx + hydrocarbons + O2 → PAN (peroxyacetyl nitrate)

Question 54

Role of NO and NO2 in acid rain

Answer 54

NO2 + H2O → HNO3 + HNO2 (nitric and nitrous acid)

Question 55

Oxidation of SO2 to sulfuric acid

Answer 55

SO2 + NO2 → SO3 + NO, then SO3 + H2O → H2SO4