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A - Chemistry > Unit 2: Section 3 - period 3 elements CDS * > Flashcards

Unit 2: Section 3 - period 3 elements CDS * Flashcards

period 3 elements and oxides

1
Q

why is sodium more reactive than magnesium?

A

it only has to lose 1 electron to form an ion whereas magnesium loses 2.
so it requires less energy

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2
Q

what happens when sodium reacts with water?

A

it reacts vigorously with cold water, forming a molten ball on the surface, fizzing and producing H2 gas.
sodium hydroxide is produced, creating a strongly alkaline solution
2Na(s) + 2H2O(l) –> 2NaOH(aq) + H2(g)

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3
Q

what happens when magnesium reacts with cold water?

A

reacts very slowly with cold water. forming weakly alkaline solution and a thin coating of magnesium hydroxide on the surface of the metal.
magnesium hydroxide is not very soluble in water, so few hydroxide ions are produced = weak alkaline
Mg(s) + 2H2O(l) –> Mg(OH)2(aq) +H2(g)

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4
Q

what happens when magnesium reacts with steam?

A

reacts much faster than with cold water, forming magnesium oxide
Mg(s) +2H2O(g) –> MgO(s) +H2(g)

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5
Q

what happens when period 3 elements react with oxygen?

A

they form oxides

usually oxidised to their highest oxidation state = the same as their group numbers. except sulfur which forms SO2

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6
Q

what is the reaction between oxygen and sodium?

A

2Na(s) + 1/2O2(g) –> Na2O(s)

vigorous reaction in air

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7
Q

what is the reaction between oxygen and aluminium?

A

2Al(s) + 3/2O2(g) –> Al2O3(s)

slow reaction in air

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8
Q

what is the reaction between oxygen and phosphorus(V)?

A

P4(s) + 5O2(g) –> P4O10(s)

spontaneously combusts in air

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9
Q

what is the reaction between oxygen and magnesium?

A

Mg(s) + 1/2O2(g) –> MgO(s)

vigorous reaction in air

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10
Q

what is the reaction between oxygen and silicon?

A

Si(s) + O2(g) –> SiO2(s)

slow reaction in air

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11
Q

what is the reaction between oxygen and sulfur?

A

S(s) + O2(g) –> SO2(s)

burns steadily in air

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12
Q

what is the bonding of the period 3 oxides?

A

giant ionic lattice - Na2O, MgO, Al2O3
giant covalent lattice - SiO2
simple covalent molecule - P4O10, SO2

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13
Q

why do the ionic period 3 oxides have high melting points?

A

they form giant ionic lattices

strong FOA between each ion means lots of energy is required to break the bonds to melt them

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14
Q

why does magnesium oxide have the highest melting point?

A

MgO has higher melting point than Na2O because Mg forms 2+ ions, so bonds more strongly than the 1+ Na ions in Na2O

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15
Q

why does aluminium oxide have the second highest melting point?

A

the difference in electronegativity between Al and O is less than that between Mg and O, so don’t attract electrons in metal-oxygen bond as strongly

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16
Q

why does SiO2 have such a high melting point?

A

it has a giant macromolecular structure

lots of energy needed to break strong covalent bonds between atoms

17
Q

why do P4O10 and SO2 have such low melting points?

A

they form simple molecular structures

molecules bound by weak intermolecular forces which take little energy to break

18
Q

what happens when ionic oxides of Na and Mg dissolve in water?

A

the O 2- ions accept protons from the water molecules to form hydroxide ions. the solutions are both alkaline, but sodium hydroxide is more soluble in water so forms a more alkaline solution

19
Q

what happens when simple covalent oxides of phosphorus and sulfur dissolve in water?

A

they form acidic solutions
all the acids are strong so the pH is 0-2.
they will dissociate in solution, forming hydrogen ions and a negative ion

20
Q

what happens when the giant covalent structure of silicon dioxide is added to water?

A

it is insoluble in water.

it will react with bases to form salts so is classed as acidic

21
Q

what happens when aluminium oxide reacts with water?

A

it is partially ionic and partially covalent bonded, and insoluble in water
it will react with acids and bases to form salts so is amphoteric

22
Q

what is the general reaction between acids and bases?

A

acid + base –> salt + water

23
Q

what is the acid-base reaction for sodium oxide?

A

Na2O(s) + 2HCl(aq) –> 2NaCl(aq) + H2O(l)

Na2O(s) + H2SO4(aq) –> Na2SO4(aq) + H2O(l)

24
Q

what is the acid-base reaction for magnesium oxide?

A

MgO(s) + H2SO4(aq) –> MgSO4(aq) + H2O(l)

3MgO + 2H3PO4 —-> 3H2O + Mg3(PO4)2

25
Q

what is the acid-base reaction for silicon dioxide?

A

SiO2(s) + 2NaOH(aq) –> Na2SiO3(aq) + H2O(l)

it must be hot and concentrated

26
Q

what is the acid-base reaction for P4O10?

A

P4O10(s) + 12NaOH(aq) –> 4Na3PO4(aq) + 6H2O(l)

27
Q

what is the acid-base reaction for sulfur dioxide?

A

SO2(s) + 2NaOH(aq) –> Na2SO3(aq) + H2O(l)

28
Q

what is the acid-base reaction for SO3?

A

SO3(s) + 2NaOH(aq) –> Na2SO4(aq) + H2O(l)

29
Q

what is the acid-base reaction for aluminium oxide?

A

with acids
Al2O3(s) + 3H2SO4(aq) –> Al2(SO4)3(aq) + 3H2O(l)
with bases
Al2O3(s) + 2NaOH(aq) –> 3H2O(l) + 2NaAl(OH)4(aq)

A - Chemistry (26 decks)

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