topic 4: properties of period 3 elements and their oxides

Question 1

which is more reactive, sodium or magnesium? why?

Answer 1

sodium as less energy to lose 1 electron than it is to lose 2.

Question 2

1) how does sodium react with cold water?
2)observations when sodium reacts with cold water?
3)what type of solution is formed when sodium reacts with water? pH?

Answer 2

1) vigorously
2) Na floats on the surface of the water and fizzes rapidly, melting because of the heat energy released by the reaction.
Produces H2 gas
3) strongly alkaline pH 13-14

Question 3

equation for reaction of sodium with water

Answer 3

2Na + 2H2O → 2NaOH + H2

Question 4

1) how does magnesium react with cold water? observation?

Answer 4

-Reacts very slowly with cold water
-Only few bubbles of H2 are formed

Question 5

type of solution formed when magnesium reacts with water? why? pH?

Answer 5

weakly alkaline solution is formed because magnesium hydroxide is not very soluble in water so few OH- ions pH 10

Question 6

equation for reaction of magnesium with cold water

Answer 6

Mg + 2H2O → Mg(OH)2 (aq) + H2(g)

Question 7

1) how does magnesium react with steam? why?
2) equation for reaction of magnesium with steam

Answer 7

1) much faster and vigorously with steam as more energy
2) Mg(s) + H2O(g) → MgO(s) + H2 (g)

Question 8

1) how does sodium react with oxygen? conditions?
2) equation

Answer 8

1) vigorously. heated
2) 4Na(s) + O2(g) →2Na2O(s)

Question 9

1) how does magnesium react with oxygen? conditions?
2) equation for reaction of magnesium and oxygen

Answer 9

1) vigorously. heated
2) 2Mg + O2 –> 2MgO

Question 10

1) how does aluminium react with oxygen? conditions?
2) equation for reaction of aluminium and oxygen

Answer 10

1) fast. powdered aluminium
2) 4Al + 3O2 –> 2Al2O3

Question 11

-how does silicon react with oxygen? conditions?
-equation for reaction of silicon and oxygen

Answer 11

-slowly. powdered and heated strongly
-Si + O2 –> SiO2

Question 12

-how does phosphorus react with oxygen? conditions?
-equation for reaction of phosphorus and oxygen

Answer 12

-spontaneously combusts. heated
-4P + 5O2 –> P4O10

Question 13

flame colour when Mg, Al, Si and P burn in oxygen?

Answer 13

white

Question 14

flame colour when sodium burns in oxygen?

Answer 14

yellow

Question 15

flame colour when Mg, Al, Si and P burn in oxygen?

Answer 15

white

Question 16

-flame colour when sulfur burns in oxygen?
-equation for reaction of sulfur and oxygen

Answer 16

-blue
-S + O2 –> SO2

Question 17

observation of what forms when Na and Mg react with oxygen?

Answer 17

white solid

Question 18

observation of what forms when Al and Si react with oxygen?

Answer 18

white solid smoke powder

Question 19

what is released when S reacts with oxygen?
equation for reaction of sulfur and oxygen

Answer 19

toxic fumes of acidic choking gas
S + O2 –> SO2

Question 20

observation of what forms when P reacts with oxygen?
equation for reaction of phosphorus and oxygen

Answer 20

white clouds
4P + 5O2 –> P4O10

Question 21

why does aluminium seem unreactive?

Answer 21

it is always coated with a strongly bonded surface layer of oxide which protects it from further reaction

Question 22

explain the trend in boiling points between Na2O and MgO

Answer 22

MgO is higher than Na2O because Mg forms a 2+ ion and the Na is only a 1+ ion so the ionic bonding is stronger.

Question 23

trend in melting point of the highest oxides of the elements Na-S - Na2O MgO Al2O3

Answer 23

-High melting points
-Giant ionic lattices
-Strong electrostatic forces of attraction between positive and negative ions
-MgO is higher than Na2O because Mg forms a 2+ ion so the ion bonding is stronger
-Al2O3 is lower than MgO because there is some covalent character. There is a smaller difference in electronegativity between Al and O than Mg and O, so the O ions do not attract the electrons as strongly.

Question 24

trend in melting point of the highest oxides of the elements - SiO2

Answer 24

-Forms a giant covalent macromolecular structure
-High melting point due to the strong covalent bonds that have to be broken

Question 25

trend in melting point of the highest oxides of the elements -

Answer 25

-Form simple molecular structures -Low melting points due to the weak intermolecular forces (van der waals and dipole-dipole) which take little energy to break -P4O10 is a bigger molecule so there are more electrons so more van der waals -SO3 is slightly bigger than SO2

Question 26

which are the: -basic oxides -insoluble oxides -amphoteric oxides -acidic oxides

Answer 26

-Na2O and MgO -Al2O3 and SiO2 -Al2O3 -SiO2, P4O10, SO2, SO3

Question 27

equation for reaction of Na2O and MgO with water and the pH of the solution formed

Answer 27

BASIC OXIDES 1) Na2O(s) + H2O(l) →2NaOH(aq) Strongly alkaline solution pH 12-14 2) -MgO(s) + H2O(l) → Mg(OH)2(s) -Mg(OH)2(s) ⇌ Mg2+(aq) + 2OH-(aq) Alkaline solution pH 9

Question 28

why are Al2O3 and SiO2 insoluble in water?

Answer 28

high lattice enthalpies (silicon dioxide has strong covalent bonds)

Question 29

-equation for reaction of P4O10 in water and pH of solution formed -dissociation equation following reaction of P4O10 in water

Answer 29

ACIDIC OXIDES -Simple covalent oxides form an acidic solution which then dissociates in solution - P4O10(s) + 6H2O(l) →4H3PO4(aq) - H3PO4(aq) ⇌ 3H+(aq) + PO43-(aq) Strong acid pH 1-2 (3) SO3(l) + H2O(l) →H2SO4(aq) (4) H2SO4(aq) ⇌ 2H+(aq) + SO42-(aq) Strong acid pH 0-1

Question 30

equation for reaction of SO2 in water and pH of solution formed dissociation equation following reaction of SO2 in water

Answer 30

- SO2(g) + H2O(l) →H2SO3(aq) - H2SO3(aq) ⇌ 2H+(aq) + SO32-(aq) Weak acid pH 2-3

Question 31

equation for reaction of SO3 in water and pH of solution formed dissociation equation following reaction of SO3 in water

Answer 31

-SO3(l) + H2O(l) →H2SO4(aq) 0-1 -H2SO4(aq) ⇌ 2H+(aq) + SO42-(aq)

Question 32

word equation for reactions of acids and bases

Answer 32

acid + base → salt + water

Question 33

which oxides react with acids?

Answer 33

basic oxides Na2O and MgO and Al2O3

Question 34

(1) ionic equation for reaction of sodium oxide with an acid (2) equation for reaction of sodium oxide and HCl

Answer 34

1) Na2O + 2H+ →2Na+ + H2O 2) Na2O + 2HCl →2NaCl + H2O

Question 35

(1) ionic equation for reaction of magnesium oxide with an acid (2) equation for the reaction of magnesium oxide and H2SO4

Answer 35

1) MgO + 2H+ →Mg2+ + H2O 2) MgO + H2SO4 →MgSO4 + H2O

Question 36

what does amphoteric oxides react with?

Answer 36

AMPHOTERIC OXIDES NEUTRALISE ACIDS AND BASES Al2O3 reacts with acids and bases

Question 37

(2) ionic equation for the reaction of aluminium oxide with an acid (1) equation for the reaction of aluminium oxide with HCl

Answer 37

1) Al2O3 + 6H+ → 2Al3+ + 3H2O 2) Al2O3 + 6HCl → 2AlCl3 + 3H2O

Question 38

which oxides react with bases?

Answer 38

acidic oxides SiO2, P4O10, SO2 and SO3 and amphoteric oxide Al2O3

Question 39

ionic equation for the reaction of silicon dioxide with a base

Answer 39

SiO2 + 2OH- →SiO32- + H2O

Question 40

equation for the reaction of silicon dioxide with NaOH

Answer 40

SiO2 + 2NaOH →Na2SiO32- + H2O

Question 41

ionic equation for the reaction of phosphorous pentoxide with a base

Answer 41

P4O10 + 12OH- →4PO43- + 6H2O

Question 42

ionic equation for the reaction of sulfur dioxide with a base

Answer 42

SO2 + 2OH- → SO32- + H2O

Question 43

equation for the reaction of sulfur dioxide with NaOH

Answer 43

SO2 + 2NaOH → Na2SO3 + H2O

Question 44

equation for the reaction of phosphorous pentoxide with NaOH

Answer 44

P4O10 + 12NaOH →4Na3PO4 + 6H2O

Question 45

ionic equation for the reaction of sulfur trioxide with a base

Answer 45

SO3 + 2OH- →SO42- + H2O

Question 46

equation for the reaction of sulfur trioxide with NaOH

Answer 46

SO3 + 2NaOH → Na2SO4 + H2O

Question 47

ionic equation for the reaction of aluminium oxide with a base

Answer 47

Al2O3 + 2OH- + 3H2O → 2Al(OH)4-

Question 48

equation for the reaction of aluminium oxide with NaOH

Answer 48

Al2O3 + 2NaOH + 3H2O → 2NaAl(OH)4