Equal masses (1.00 g) of three Group 1 metals—lithium, sodium, and potassium—are reacted completely with excess water in three separate open beakers. Which of the following statements correctly compares the observations or chemical outcomes of these reactions?
Lithium produces the greatest total volume of hydrogen gas because it has the lowest relative atomic mass of the three metals, resulting in the highest number of moles of metal reacting.
Potassium reacts the fastest because it has the highest first ionisation energy of the three metals, allowing it to lose its outer electron most easily.
Sodium produces the greatest total volume of hydrogen gas because its intermediate reactivity allows a more stable and complete reaction with water.
Lithium reacts the fastest of the three metals because it has the most negative standard electrode potential (E∘=−3.04 VE^\circ = -3.04\text{ V}E∘=−3.04 V), making the reaction thermodynamically most favourable.
75 exam-style questions on Edexcel GCSE Chemistry 7.1 Group 1, covering 7.1.1 Classifying elements by group in the periodic table and 7.1.2 Properties and reactions of the alkali metals. Each one has a worked solution and a mark scheme showing where the marks go.