Question

Two drops of dilute sulphuric acid were added to 1 g of copper sulfate powder and then a small amount of hot water was added to dissolve it (step I). On cooling, beautiful blue-colored crystals got separated (step II). Step I and Step II are:

• A. physical and chemical changes, respectively
• B. chemical and physical changes, respectively.
• C. both physical changes.
• D. both chemical change

Answer 1

The correct option is C

both physical changes.

The explanation for correct option:

C. both physical changes

The reaction of Copper sulfate with sulfuric acid:

Step 1:

• Two drops of dilute sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ were added to 1 g of copper sulfate$\left({\mathrm{CuSO}}_4\right)$ powder and then a small amount of hot water was added to dissolve it.
• The chemical reaction can be depicted as:
• ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)\stackrel{\mathrm{conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$
• This change is a physical change as no new chemical is formed.

Step 2:

• On cooling, beautiful blue-colored crystals got separated.
• This change is considered a physical change i.e. "A change in which a substance undergoes a change in its physical properties is called a physical change.”

The explanation for incorrect options:

As the reaction of dilute sulfuric acid with copper sulfate along with hot water and the blue-colored crystals so formed is a physical change. Thus options A, B, and D are incorrect.

Hence, the correct option is C i.e. both physical changes.