Elemental magnesium reacts with excess 1.0 M HCl(aq) to produce H₂(g). Four separate experiments are summarized below.
Experiment
Form of Mg(s)
Temperature (°C)
Concentration of HCl (M)
Added Substance
A
Ribbon
25
1.0
None
B
Powder
25
1.0
None
C
Ribbon
40
1.0
None
D
Ribbon
25
1.0
0.010 M Na₂SO₄ (acts as an inhibitor by forming a surface layer)
All experiments use the same mass of Mg.
(a) Based on the information provided, rank the experiments from fastest to slowest rate of H₂ production. Express your answer in the form "___ > ___ > ___ > ___."
(b) Between Experiments B and C, which experimental change has the greater effect on the rate? Explain your reasoning, citing relevant kinetic principles.
(c) For Experiment D, explain why the rate decreases compared with Experiment A even though all intensive variables other than the added substance are identical.