1.
(a) $BaCl_2(aq)$ $+$ $Na_2SO_3(aq)$ $\rightarrow$ $BaSO_3(s)$ $+$ $2NaCl(aq)$. (White ppt: Barium
Sulphite).
(b) Precipitation Reaction or Double Displacement.
(c) $BaSO_3(s)$ $+$ $2HCl(aq)$ $\rightarrow$ $BaCl_2(aq)$ $+$ $H_2O(l)$ $+$ $SO_2(g)$. White ppt disappears
due to formation of soluble Barium Chloride.
2.
(a) M is Iron (Fe). G is Hydrogen gas ($H_2$). Iron reacts with steam but not cold/hot water.
(b) $3Fe(s)$ $+$ $4H_2O(g)$ $\rightarrow$ $Fe_3O_4(s)$ $+$ $4H_2(g)$.
(c) Yes. $Fe + 2HCl \rightarrow FeCl_2 + H_2$.
3.
(a) X: Zinc ($Zn$). Y: Sulphuric acid ($H_2SO_4$). Z: Hydrogen ($H_2$).
(b) $Zn$ $+$ $H_2SO_4$ $\rightarrow$ $ZnSO_4$ $+$ $H_2$.
(c) 'Pop' sound test with burning matchstick.
4.
(a) X is Limestone or Calcium Carbonate ($CaCO_3$).
(b) $CaCO_3$ $+$ $H_2SO_4$ $\rightarrow$ $CaSO_4$ $+$ $H_2O$ $+$ $CO_2$. (Reaction releasing gas).
$Ca(OH)_2$ $+$ $CO_2$ $\rightarrow$ $CaCO_3$ $+$ $H_2O$ (Turning lime water milky).
$CaCO_3$ $+$ $H_2O$ $+$ $CO_2$ $\rightarrow$ $Ca(HCO_3)_2$ (Milkiness disappears).
5.
Reaction will take place in Beaker A (Iron nail in Copper sulphate).
Because Iron is more reactive than Copper, it displaces Copper.
$Fe(s)$ $+$ $CuSO_4(aq)$ $\rightarrow$ $FeSO_4(aq)$ $+$ $Cu(s)$.
6.
(a) Corrosion (specifically Sulphidation). Silver reacts with Sulphur in air.
(b) Silver Sulphide ($Ag_2S$).
7.
(a) Green color fades to white, then reddish-brown. Smell of burning sulphur.
(b) Thermal Decomposition.
(c) 7 molecules ($FeSO_4 \cdot 7H_2O$).
$$2FeSO_4(s)$$ $\xrightarrow{\Delta}$ $Fe_2O_3(s)$ $+$ $SO_2(g)$ $+$ $SO_3(g)$.
8.
Oxidizing agent: $MnO_2$ (Mn goes from +4 to 0, reduced). Reducing agent: $Al$ (Al goes from 0 to +3,
oxidized).
Process: Thermite Reaction. Aluminium is a strong reducing agent and the reaction releases
immense heat (exothermic) to melt iron for welding.
9.
(a) Anode: Oxygen ($O_2$). Cathode: Hydrogen ($H_2$).
(b) Water ($H_2O$) contains 2 atoms of Hydrogen for every 1 atom of Oxygen. Mole ratio is 2:1.
(c) Electrolysis would be very slow or negligible as pure water is a poor conductor.
10.
(a) Yellow precipitate. Lead Iodide ($PbI_2$).
(b) No. Ions are not free to move in solid state, so double displacement cannot occur.
11.
To prevent Photolytic Decomposition. Silver Chloride decomposes into Silver and Chlorine in
the presence of sunlight.
12. Oxidation of fats and oils.
13. Nitrogen gas.
14. BHA (Butylated Hydroxyanisole) and BHT (Butylated Hydroxytoluene).
15. (Heat): $CaCO_3$ $\xrightarrow{\Delta}$ $CaO$ $+$ $CO_2$.
16. (Light): $2AgBr$ $\xrightarrow{Sunlight}$ $2Ag$ $+$ $Br_2$.
17. (Electricity): $2H_2O$ $\xrightarrow{Electricity}$ $2H_2$ $+$ $O_2$.
