4 (a) Copper carbonate reacts with dilute nitric acid - Edexcel - GCSE Chemistry Combined Science - Question 4 - 2021 - Paper 1

When the pH changes from 2 to 6, it indicates a decrease in the concentration of hydrogen ions. The relationship between pH and hydrogen ion concentration is given by the formula:

$[H^+] = 10^{-pH}$

Thus, for pH 2, the concentration is: $[H^+]_2 = 10^{-2} = 0.01 ext{ M}$

And for pH 6, we have: $[H^+]_6 = 10^{-6} = 0.000001 ext{ M}$

To find the factor change:

ext{Factor} = rac{[H^+]_2}{[H^+]_6} = rac{0.01}{0.000001} = 10000

Thus, the correct answer is A x 10000.

To obtain copper sulfate crystals from a copper sulfate solution, follow these steps:

1. Evaporation: Heat the solution gently to evaporate some of the water. This will increase the concentration of the copper sulfate in the solution.

2. Cooling: Allow the concentrated solution to cool slowly. As the solution cools, the solubility of copper sulfate decreases, causing it to crystallize out of the solution.

3. Separation: Once crystals have formed, filter the solution to separate the crystals from the liquid.

4. Drying: Finally, place the filtered crystals on a filter paper or drying surface to remove any remaining moisture.