An investigation was carried out to study the displacement reactions of various metals with nickel(II) chloride solution.
A student measured 100 cm3 of nickel(II) chloride solution into an insulated polystyrene cup. After recording the initial temperature of the solution, they added a fixed mass of a metal powder and recorded the maximum temperature change achieved.
Table 1 shows the experimental results obtained:
| Metal | Temperature change (∘C^{\circ}\text{C}∘C) |
|---|---|
| Chromium | +9.5 |
| Silver | 0.0 |
| Calcium | +34.5 |
Identify the independent variable and the dependent variable in this investigation.
Arrange the three metals in order of decreasing reactivity (from most reactive to least reactive).
The reaction profile for the displacement reaction between calcium and nickel(II) chloride solution is shown below.
Which letter represents the activation energy, and which letter represents the reactants?