1. (a)
X is Baking Soda. (b) $NaHCO_3$. (c)
$2NaHCO_3(s) \xrightarrow{\Delta} Na_2CO_3(s) + H_2O(g) + CO_2(g)$
2. X is Sodium Hydrogen Carbonate ($NaHCO_3$, Baking Soda).
Y is Sodium Carbonate ($Na_2CO_3$, Washing Soda).
3. A is Baking Soda ($NaHCO_3$). B is
Sodium Carbonate ($Na_2CO_3$). C is Carbon Dioxide ($CO_2$).
4. (a) Lime water turns milky. (b)
$CaCO_3(s) + 2HCl(aq) \rightarrow CaCl_2(aq) + H_2O(l) + CO_2(g)$
$Ca(OH)_2(aq) + CO_2(g) \rightarrow CaCO_3(s) + H_2O(l)$
5. The salt is Plaster of Paris ($CaSO_4 \cdot \frac{1}{2}H_2O$). It absorbs
water from atmosphere and sets into Gypsum ($CaSO_4 \cdot 2H_2O$), a hard solid.
$CaSO_4 \cdot \frac{1}{2}H_2O + \frac{3}{2}H_2O \rightarrow CaSO_4 \cdot 2H_2O$
6. (a)
X is Plaster of Paris. (b)
$CaSO_4 \cdot 2H_2O \xrightarrow{373K} CaSO_4 \cdot \frac{1}{2}H_2O + \frac{3}{2}H_2O$
7. (a) Neutral: D (pH 7). (b) Strongly Alkaline: C (pH 11). (c) Strongly
Acidic: B (pH 1). (d) Weakly Acidic: A (pH 4). (e) Weakly Alkaline: E (pH 9).
Increasing $H^+$ concentration: C < E < D < A < B.
8. $NaCl$ is a salt of strong acid (HCl) and strong base (NaOH), so
it's neutral. $Na_2CO_3$ is a salt of weak acid ($H_2CO_3$) and strong base (NaOH), so it's basic.
9. (a) Blue-green solution of $CuCl_2$ is formed.
$CuO(s) + 2HCl(aq) \rightarrow CuCl_2(aq) + H_2O(l)$
(b) Black to Blue-green. (c) Metallic oxides are basic in nature.
10. Calcium Sulphate Hemihydrate, $CaSO_4 \cdot \frac{1}{2}H_2O$.
Prepared by heating Gypsum at 373K. PoP is hygroscopic and absorbs moisture from air, becoming
Gypsum (useless).
$CaSO_4 \cdot 2H_2O \xrightarrow{373K} CaSO_4 \cdot \frac{1}{2}H_2O +
\frac{3}{2}H_2O$
11. Fixed number of water molecules present in one formula unit of a
salt. Examples: Blue Vitriol ($CuSO_4 \cdot 5H_2O$), Washing Soda ($Na_2CO_3 \cdot 10H_2O$).
12. (a) Anode: Chlorine ($Cl_2$). Used for: Water purification, PVC,
disinfectants. (b) Cathode: Hydrogen ($H_2$). Used for: Ammonia production, fuels, hydrogenation.
(c) Near cathode: Sodium Hydroxide ($NaOH$).
13. Color will be Red/Orange (acidic). On adding NaOH, it will shift
through Orange -> Yellow -> Green (at pH 7) -> Blue -> Violet/Purple (basic).
14. (a) Acids dissociate in water to produce $H^+$ ions which are
mobile charge carriers. (b) No. Dry HCl does not have free $H^+$ ions; water is needed for
dissociation.
15. pH will decrease (become more acidic). Lactobacillus bacteria
produce Lactic Acid from lactose, increasing $H^+$ ion concentration.
16. On dilution, the concentration of $H_3O^+$ ions per unit volume
decreases. Total number of ions remains constant, but they are spread in a larger volume.
17. The concentration of $OH^-$ ions increases as more base (NaOH)
dissolves, releasing more hydroxide ions.
