Question

Question 3: In a lab experiment, you are tasked with determining the electrochemical reaction that can occur between aqueous hydrochloric acid (HCl)) and solid magnesium metal (Mg). When the magne- sium is placed in solution, gas bubbles begin to appear around the metal and evolve from solution. (a) Write out the two half reactions that occur when the magnesium is placed in the hydrochloric acid solution. Which species is the getting oxidized? Reduced? (b) Which species is acting as the cathode? The anode? (c) Why do bubbles appear in the solution after the magnesium is added? In the lab, how might you confirm your hypothesis? (d) Which species in this system has the higher electrochemical potential? (e) Without looking up any values or doing any calculations - is the potential of this cell positive or negative? Why?

Answer 1

a) anodic half reaction is Mg------} Mg⁺² + 2e^- ( and Mg gets oxidzed)

cathodic half reaction is 2H⁺ + 2e^- -----------} H₂ (g) ( and H⁺ gets reduced)

b) cathodic species is H⁺

anodic species is Mg

c) Bubbles produced due to the fromation of H₂ gas

d) it is Mg

e) Yes it is positive. Because in the electrochemical series the Mg metal is place above the H. So when Mg is in contact with H it replace th H and gives products with positive EMF values.