Question

Which of the following can be oxidised by $SO_2$ ?

• A. $K_2Cr_2O_7$
• B. $Mg$
• C. $H_2O$
• D. All of these

Answer 1

Answer: (B)

With $K _2 Cr _2 O _7, SO _2$ works as reducing agent.
$K _2 Cr _2 O _7+ H _2 SO _4+3 SO _2 \longrightarrow K _2 SO _4+ Cr _2\left( SO _4\right)_3+ H _2 O$
With water the reaction is not a redox reaction,
$SO _2+ H _2 O \longrightarrow H _2 SO _3$
$2 Mg + SO _2 \longrightarrow 2 MgO + S $
$3 Mg + SO _2 \longrightarrow 2 MgO + MgS$