Atoms and reactions

Which reaction is a redox reaction?

$K2Cr2O7+2KOH→2K2CrO4+H2O\text{K}_2\text{Cr}_2\text{O}_7 + 2\text{KOH} \rightarrow 2\text{K}_2\text{CrO}_4 + \text{H}_2\text{O}$

$2FeCl3+H2S→2FeCl2+S+2HCl2\text{FeCl}_3 + \text{H}_2\text{S} \rightarrow 2\text{FeCl}_2 + \text{S} + 2\text{HCl}$

$Al2O3+6HNO3→2Al(NO3)3+3H2O\text{Al}_2\text{O}_3 + 6\text{HNO}_3 \rightarrow 2\text{Al}(\text{NO}_3)_3 + 3\text{H}_2\text{O}$

$AgNO3+NaCl→AgCl+NaNO3\text{AgNO}_3 + \text{NaCl} \rightarrow \text{AgCl} + \text{NaNO}_3$

Atoms and reactions Questions

Which reaction is a redox reaction?

$K2Cr2O7+2KOH→2K2CrO4+H2O\text{K}_2\text{Cr}_2\text{O}_7 + 2\text{KOH} \rightarrow 2\text{K}_2\text{CrO}_4 + \text{H}_2\text{O}$

$2FeCl3+H2S→2FeCl2+S+2HCl2\text{FeCl}_3 + \text{H}_2\text{S} \rightarrow 2\text{FeCl}_2 + \text{S} + 2\text{HCl}$

$Al2O3+6HNO3→2Al(NO3)3+3H2O\text{Al}_2\text{O}_3 + 6\text{HNO}_3 \rightarrow 2\text{Al}(\text{NO}_3)_3 + 3\text{H}_2\text{O}$

$AgNO3+NaCl→AgCl+NaNO3\text{AgNO}_3 + \text{NaCl} \rightarrow \text{AgCl} + \text{NaNO}_3$