(3ai)
This can be defined as the number of atoms or molecules in one mole of a substance which is equal to 6.02 ×10²³
(3aii)
Mass/m.m = no. of molecules/Avogadro’s number
(2.30/m.m) × (3.01×10²²/6.02×10²³)
m.m = (2.30×6.02×10²³)/3.01×10²²
m.m = 46g/mol
(3aiii)
Since the molar mass = 46g/mol
The formula is NO₂
:. 14+(16×2)
14+32 = 46g/mol
:. NO₂
(3bi)
(i) There is no reaction but rather forms a layer underneath the water
(ii) It reacts violently with water forming white silicon dioxide and hydrogen chloride gas.
(3bii)
The reaction is different because CCl₄ is an organic substance while SiCl₄ is not.
(3ci)
Extraction of copper
(3cii)
(i) CuSO₄
(ii) CuCl₂
(3ciii)
Cu²⁺ + 2e⁻ —> Cu
(3civ)
Using; m = ZIt
Z = m/It
Z = 3.2/(50x(3×60)+13)
Z = 3.2/(50×193)
Z = 3.2/9650
Z = 0.000332g/Asec
(3d)
Oxygen can be prepared by heating KClO₃ in the presence of manganese(iv)oxide which acts as a catalyst to produce KCl and oxygen gas. The reaction takes place at a lower temperature and much faster rate.
KClO₃ (MnO₂)heat—–> KCl + O₂