Equal lengths of magnesium ribbon are taken in two test tubes $A$ and $B$. $H_{2}SO_{4}$ is added to test tube $A$ and $H_{2}CO_{3}$ is added to test tube $B$ in equal amounts.
$(a)$ Write chemical equations for both the reactions.
$(b)$ Out of the two acids taken above,which one will have a lower $pH$ value and lower $H^{+}$ concentration,respectively?

(B) The chemical equations for the reactions are:
$Mg(s) + H_{2}SO_{4}(aq) \rightarrow MgSO_{4}(aq) + H_{2}(g)$
$Mg(s) + H_{2}CO_{3}(aq) \rightarrow MgCO_{3}(s) + H_{2}(g)$
$(b)$ $H_{2}SO_{4}$ is a strong acid,while $H_{2}CO_{3}$ is a weak acid.
Therefore,$H_{2}SO_{4}$ will have a lower $pH$ value because it dissociates completely to provide a higher concentration of $H^{+}$ ions.
Conversely,$H_{2}CO_{3}$ will have a lower $H^{+}$ concentration because it is a weak acid and dissociates only partially.