In an experiment, nickel oxide is added to sulfuric acid until no more nickel oxide reacts - Scottish Highers Chemistry - Question 19 - 2023

To correctly separate and collect a dry, pure sample of nickel sulfate from the reaction between nickel oxide and sulfuric acid, the first step is filtration. This process removes any unreacted nickel oxide and other insoluble impurities from the mixture, leaving behind the nickel sulfate solution.

After filtration, the next step is evaporation. This phase of the process involves heating the nickel sulfate solution to evaporate the water, resulting in the formation of dry nickel sulfate crystals. Therefore, option C, 'filtration followed by evaporation', is the best method to achieve the desired outcome.