Oxides + Reactions w/ Water
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What type of structure does sodium oxide (Na₂O) have, does this affect its melting point? (gnt. inc. ltcs. w/ strng. elctrs. frcs. btwn. opp. chrgd. ins. - rqrng. lrg. amnt. enrgy. brk. - hs. hgh. mltng. pnt.)
It has a giant ionic lattice with strong electrostatic forces between oppositely charged ions, requiring a large amount of energy to break, so it has a high melting point
Why do magnesium oxide (MgO) and aluminium oxide (Al₂O₃) have high melting points? (hve. gnt. ion. ltcs. w/ strng. elctrstc. atrtns. btwn. ins. rrng. lrg. amnts. enrgy. brk.)
They have giant ionic lattices with strong electrostatic attractions between ions, requiring large amounts of energy to break
Which oxides form giant structures?
Na₂O, MgO, Al₂O₃, and SiO₂
What structure does silicon dioxide (SiO₂) have and why does it have a high melting point? (hs. gnt. cvlnt. trtctr. w/ mny. stng. cvlnt bnd. rqre. lt. enrgy. brk. gvng. hgh. mltng. pnt.)
It has a giant covalent structure with many strong covalent bonds that require a lot of energy to break giving to a high melting point
Why does P₄O₁₀ have a lower melting point than SiO₂? (P smp. mlclr. sbstnc. w/ wk. intrmlcr. frc. whrs. S hs. strng. cvlnt. bnds. thrht. gnt. strtcr.)
P₄O₁₀ is a simple molecular substance with weak intermolecular forces, whereas SiO₂ has strong covalent bonds throughout a giant structure
What is the difference in polarity between SO₂ and SO₃?
SO₂ is polar, while SO₃ is non-polar
Why does SO₃ have a higher melting point than SO₂? (SO3 >ox. atms. - >elctrns. - ldng. strngr. vdw frcs. dspte. bng. n.plr)
SO₃ has more oxygen atoms, so more electrons, leading to stronger van der Waals forces, despite being non-polar
Why do giant lattices have higher melting points than molecular substances? (strng. bnds. mst. brkn. rthr. thn. WIMF)
Because strong bonds (ionic or covalent) must be broken, rather than weak intermolecular forces
Why does aluminium oxide have some covalent character? (A ins. smll. w/ hgh. chrg. dnsty. - plrs. O ins. gvng. prtl. cvlnt. chrctr.)
Aluminium ions are small with a high charge density, so they polarise the oxygen ions, giving partial covalent character
Why does silicon dioxide not react with water? (wtr. cnt. brk. strng. cvlnt. bnds. - gnt. clvnt. strctr. - insol.)
Water cannot break the strong covalent bonds in its giant covalent structure, so it is insoluble
Why does aluminium oxide not react with water? (bndng. strng. + dnt. dsct. - insol.)
The bonding is very strong and ions do not dissociate, so it is insoluble
What happens when sodium oxide reacts with water? (dslvs. + dscts. - O rcts. w/ wtr. frm. OH - prdcng. strngly. alk. sltn.)
It dissolves and dissociates into Na⁺ and O²⁻ ions; O²⁻ reacts with water to form OH⁻, producing a strongly alkaline solution
What is the pH of a solution formed from sodium oxide?
Approximately 13–14
What happens when magnesium oxide reacts with water and what is the pH? (frms. mag. hydr. sprgly. sol. | 9-10)
It forms magnesium hydroxide, which is sparingly soluble, giving a pH of about 9–10
What is formed when P₄O₁₀ reacts with water and what is the pH? (phsprc. acd. |1-2)
Phosphoric acid (H₃PO₄) is formed, with a pH of about 1–2
Draw H₃PO₄
Draw the phosphate (IV) ion, name shape and bond angle
What happens when sulfur dioxide reacts with water? (frm. slfrs. acd. | 2-3)
It forms sulfurous acid (H₂SO₃), with a pH of about 2–3
What happens when sulfur trioxide reacts with water? (rcts. vgrlsy. frm. slfrc. acd. w/ 0-1)
It reacts vigorously to form sulfuric acid (H₂SO₄), with a pH of 0–1
Draw, name the shape and deduce the bond angle of the sulfate ion (SO₄²⁻)?
Tetrahedral with a bond angle of 109.5°
Draw, name the shape and deduce the bond angle of the sulfite (IV) ion (SO₃²⁻)?
Trigonal pyramidal with a bond angle of about 107°