The pair that does NOT require calcination is :

Options

A. `ZnO and MgO`
B. `Fe_(2)O_(3) and CaCO_(3).MgCO_(3)`
C. `ZnO and Fe_(2)O_(3).xH_(2)O`
D. `ZnCO_(3) and CaO`

Answer

To solve the question regarding which pair does NOT require calcination, we can follow these steps:

### Step 1: Understand Calcination
Calcination is defined as the process of heating a solid material to a high temperature in the absence of air or oxygen, primarily to remove volatile substances, such as water or carbon dioxide. This process is commonly applied to carbonates, which decompose into oxides and carbon dioxide upon heating.

**Hint:** Remember that calcination is specifically important for carbonates and other compounds that release gases upon heating.

### Step 2: Identify the Compounds in the Options
In the question, we are given a pair of compounds. Let's consider the pair ZnO (zinc oxide) and MgO (magnesium oxide). Both of these compounds are oxides.

**Hint:** Focus on the chemical nature of the compounds. Are they oxides, carbonates, or something else?

### Step 3: Analyze the Need for Calcination
Since ZnO and MgO are already in oxide form, they do not contain any volatile components that would be released upon heating. Therefore, there is no need for calcination for these compounds, as they will not decompose or change in structure.

**Hint:** Consider what happens to carbonates when heated. Do ZnO and MgO behave similarly?

### Step 4: Compare with Other Pairs
In contrast, if we were to consider carbonates like CaCO3 (calcium carbonate) or MgCO3 (magnesium carbonate), these would decompose upon calcination to form their respective oxides and release carbon dioxide gas.

**Hint:** Think about what happens to carbonates when they undergo calcination.

### Step 5: Conclusion
Thus, the pair that does NOT require calcination is indeed ZnO and MgO, as they are already in their stable oxide forms and do not undergo any further decomposition.

**Final Answer:** The pair that does NOT require calcination is ZnO and MgO.