MCAT Chemistry Question — Alkali Metals & Water
- Mar 18, 2017
- MCAT Question of the Day
2M(s) + 2H2O(l) → 2MOH(aq) + H2(g)
Which of the following alkali metals will react the most violently with water?
Click for Explanation
To choose between sodium and cesium, you must apply the periodic table trends for ionization energy. Since the metal M loses an electron in the reaction with water, the metal that is the most easily oxidized will be the most reactive. The trend for ionization energy increases going up and to the right in the periodic table, which makes cesium the more easily oxidized element. Thus, D is the correct answer. If this does not make sense, think of it this way – the lower the ionization energy, the easier it is to remove an electron from the species, and the more reactive the species will be. Cesium, which is nearest the bottom left of the periodic table, has the lowest ionization energy of the given choices.
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