In what form occurs chlorhydric acid in water?
It is dissociated to $H^+$ ions (colourless) and $Cl^-$ (colourless).
What happens with the $H^+$ ion?
Two $H^+$ ions are reduced to $H_2$ (colourless gas, explosive when mixed with air ).
What happens with metallic $Zn$ ?
It is oxidised to $Zn^{2+}$ ion (colourless).
What role do the $2H^+$ ions play?
They are oxidants because they catch electrons.
What role does $Zn$ play?
It the reductant because it gives electrons away.
Write the partial equations representing the half reactions of oxidation and reduction, followed by the complete redox reaction!
$2H^+$ $+$ $2e^-$ $\longrightarrow$ $H_2$
$Zn$ $-$ $2e^-$ $\longrightarrow$ $Zn^{2+}$
$2H^+$ $+$ $Zn$ $\longrightarrow$ $H_2$ $+$ $Zn^{2+}$
Complete for the ions which are not involved et annotate!
$2H^+$ $+$ $2Cl^-$ $+$ $Zn$ $\longrightarrow$ $H_2$ $+$ $Zn^{2+}$ $+$ $2NO_3^-$ Chlorhydric acid and zinc produce hydrogen and a solution of zinc nitrate.