CHEMISTRY · Single correct · A Level · Chemistry · Group 2 elements (alkaline earth metals) · Group 2 elements (alkaline earth metals)
Problem
Equal masses of Mg(s), Ca(s), and Sr(s) are separately added to excess 1.0MHCl at 25 °C. Bubbles of H2(g) form in each beaker. Assuming surface-area effects are negligible, which metal is expected to produce hydrogen gas at the greatest initial rate, and why?
(a) Mg, because an equal mass contains the greatest number of atoms, producing H2 faster.
(b) Sr, because its low first-ionization energy makes oxidation of the metal atoms easiest.
(c) Mg, because its high first-ionization energy makes it especially reactive toward HCl.
(d) Ca, because its properties are intermediate, giving the most favorable combination of size and molar quantity for reaction.