Assertion: The impurities such as SiO2 present in iron ore is removed by CaCO3.
Reason: CaO formed by decomposition of CaCO3 reacts with SiO2 to form slag.
The CaO formed acts as a flux which reacts with silica (SiO2) to form fusible slag. The reaction involved is:
CaO(s)+ SiO2(s) →CaSiO3(l)
The slag melts near the zone of fusion and forms a protective liquid layer. This prevents molten iron from getting oxidised.