KEY to Sample Problems Chapter 10

KEY to Sample Problems – Chapter 10

1. (a) sulfur dioxide or sulfur(IV) oxide

(b) dialuminum trioxide or aluminum oxide

(d) dinitrogen tetroxide or nitrogen(IV) oxide

(e) dilithium oxide or lithium oxide

(f) cobalt oxide or cobalt(II) oxide

(g) titanium dioxide or titanium(IV) oxide

(h) tungsten trioxide or tungsten(VI) oxide

(i) potassium hydroxide

(j) manganese(II) hydroxide

(k) iron(III) hydroxide

(l) aluminum hydroxide

2. (a) NO (b) N2O (c) N2O3 (d) N2O5

(e) P2O5 (f) Rb2O (g) Fe2O3 (h) Na2O

(i) Al2O3 (j) CoO (k) Co2O3 (l) OsO4

(m) Re2O7 (n) ReO3 (o) MoO3 (p) BeO

3. (a) Zn + 2HClO3 ® Zn(ClO3)2 + H2

Zn(s) + 2H+(aq) + 2ClO3–(aq) ® Zn2+(aq) + 2ClO3–(aq) + H2(g) (total)

Zn(s) + 2H+(aq) ® Zn2+(aq) + H2(g) (net)

(b) Mg + H2SO4 ® MgSO4 + H2

Mg(s) + 2H+(aq) + SO42–(aq) ® Mg2+(aq) + SO42–(aq) + H2(g) (total)

Mg(s) + 2H+(aq) ® Mg2+(aq) + H2(g) (net)

(d) Hg + HNO3 ® no reaction

(e) Ni + 2HNO3 ® Ni(NO3)2 + H2

Ni(s) + 2H+(aq) + 2NO3–(aq) ® Ni2+(aq) + 2NO3–(aq) + H2(g) (total)

Ni(s) + 2H+(aq) ® Ni2+(aq) + H2(g) (net)

(f) 2Al + 3H2SO4 ® Al2(SO4)3 + 3H2

2Al(s) + 6H+(aq) + 3SO42–(aq) ® 2Al3+(aq) + 3SO42–(aq) + 3H2(g) (total)

2Al(s) + 6H+(aq) ® 2Al3+(aq) + 3H2(g) (net)

(g) Cd + 2HI ® CdI2 + H2

Cd(s) + 2H+(aq) + 2I–(aq) ® Cd2+(aq) + 2I–(aq) + H2(g) (total)

Cd(s) + 2H+(aq) ® Cd2+(aq) + H2(g) (net)

(h) Au + HClO3 ® no reaction

(i) Zn + Hg(NO3)2 ® Zn(NO3)2 + Hg

Zn(s) + Hg2+(aq) + 2NO3–(aq) ® Zn2+(aq) + 2NO3–(aq) + Hg(l) (total)

Zn(s) + Hg2+(aq) ® Zn2+(aq) + Hg(l) (net)

(j) Mg + CuCl2 ® MgCl2 + Cu

Mg(s) + Cu2+(aq) + 2Cl–(aq) ® Mg2+(aq) + 2Cl–(aq) + Cu(s) (total)

Mg(s) + Cu2+(aq) ® Mg2+(aq) + Cu(s) (net)

(k) Fe + NaBr ® no reaction

(l) Au + MgSO4 ® no reaction

(m) Ni + 2AgNO3 ® Ni(NO3)2 + 2Ag

Ni(s) + 2Ag+(aq) + 2NO3–(aq) ® Ni2+(aq) + 2NO3–(aq) + 2Ag(s) (total)

Ni(s) + 2Ag2+(aq) ® Ni2+(aq) + 2Ag(s) (net)

(n) Hg + FeSO4 ® no reaction

4. (a) H3O+ (b) NH4+ (c) H2O (d) HF (e) HSO4– (f) HS–

5. (a) OH– (b) NH2– (c) H2O (d) Cl– (e) HSO4– (f) PH3

6. (a) CH3COO– + H3O+ CH3COOH + H2O

base1 acid2 acid1 base2

Strongest acid – H3O

Strongest base – CH3COO–

(b) NH3 + H2O NH4+ + OH–

base1 acid2 acid1 base2

Strongest acid – NH4+

Strongest base – OH–

acid1 base2 base1 acid2

Strongest acid – HCl

Strongest base – H2O

7. Compound X is a strong base.

8. (a) The H–F bond is stronger than the H–Cl bond since F atom is smaller than Cl atom and the attraction between the atomic nuclei and the shared electron pair is stronger. It means that it is more difficult to take the H+ ion from the HF molecule than from the HCl molecule. Therefore, HCl is a stronger acid.

(b) By the same argument as in (a), the H–Cl bond is stronger than the H–I bond, and HI is a stronger acid.

(c) In H2SO3 there are 3 oxygen atoms connected to the central sulfur atom. 2 of these oxygen atoms have hydrogen atoms attached to them. The oxidation number of sulfur is +4. In H2SO4 there are 4 oxygen atoms connected to the central sulfur atom, and the oxidation number of sulfur is +6. The addition of the fourth oxygen atom leads to withdrawal of more electron density from the sulfur atom. To compensate for the lost electron density, the sulfur atom tries to pull the electrons back from the oxygen atoms that are bound to the hydrogen atoms. This makes O–H bonds more polar and H atoms become more acidic. Therefore, H2SO4 is a stronger acid.

(d) HNO3 is a stronger acid in the pair. The argument is analogous to that presented in (c).

(e) HClO2 is a stronger acid in the pair. The argument is analogous to that presented in (c).

(f) HBrO4 is a stronger acid in the pair. The argument is analogous to that presented in (c).

9. (a) NaOH + HBr ® NaBr + H2O

Na+(aq) + OH–(aq) + H+(aq) + Br–(aq) ® Na+(aq) + Br–(aq) + H2O(l) (total)

OH–(aq) + H+(aq) ® H2O(l) (net)

(b) 2NaOH + H2SO3 ® Na2SO3 + 2H2O

2Na+(aq) + 2OH–(aq) + H2SO3(aq) ® 2Na+(aq) + SO32–(aq) + 2H2O(l) (total)

2OH–(aq) + H2SO3(aq) ® SO32–(aq) + 2H2O(l) (net)

Ba2+(aq) + 2OH–(aq) + 2H+(aq) + SO42–(aq) ® BaSO4(s) + 2H2O(l) (total)

The net equation is the same as the total one.

(d) Ca(OH)2 + 2HClO3 ® Ca(ClO3)2 + 2H2O

Ca(OH)2(s) + 2H+(aq) + 2ClO3–(aq) ® Ca2+(aq) + 2ClO3–(aq) + 2H2O(l) (total)

Ca(OH)2(s) + 2H+(aq) ® Ca2+(aq) + 2H2O(l) (net)

(e) H3PO4 + 3KOH ® K3PO4 + 3H2O

H3PO4(aq) + 3K+(aq) + 3OH–(aq) ® 3K+(aq) + PO43–(aq) + 3H2O(l) (total)

H3PO4(aq) + 3OH–(aq) ® PO43–(aq) + 3H2O(l) (net)

10. (a) KOH + H3PO4 ® KH2PO4 + H2O (potassium dihydrogen phosphate)

(b) Ba(OH)2 + HBr ® Ba(OH)Br + H2O (barium hydroxobromide)

(d) 2NaOH + H2SO3 ® Na2SO3 + 2H2O (sodium sulfite)

(e) LiOH + H2SO3 ® LiHSO3 + H2O (lithium hydrogen sulfite)

(f) Ca(OH)2 + HCl ® Ca(OH)Cl + H2O (calcium hydroxochloride)

11. (a) Lewis base

(b) Lewis acid

(d) Lewis acid

(e) Lewis base

(f) Lewis acid

(g) Lewis base