Densities of diamond and graphite are `(3.5g)/(mL)` and `(2.3g)/(mL)`.
C (diamond) equilibrium C (graphite)
`Delta_(7)H=-1.9(kJ)/("mole")`
Favourable conditions for formation of diamond are:

Options

A. high pressure and low temperature
B. low pressure and high temperature
C. high pressure and high temperature
D. low pressure and low temperature

Answer

To determine the favorable conditions for the formation of diamond from graphite, we can analyze the given information step by step.

### Step 1: Understand the Reaction
The reaction we are considering is the conversion of carbon in the diamond form (C_diamond) to carbon in the graphite form (C_graphite). The equilibrium can be represented as:
\[ \text{C (diamond)} \rightleftharpoons \text{C (graphite)} \]

### Step 2: Analyze the Enthalpy Change
We are given that the enthalpy change (ΔH) for the reaction is -1.9 kJ/mol. This negative value indicates that the reaction is exothermic, meaning that heat is released when diamond is formed from graphite.

### Step 3: Apply Le Chatelier's Principle
According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the system will adjust to counteract that change.

### Step 4: Consider Temperature Effects
Since the reaction is exothermic, increasing the temperature will shift the equilibrium to favor the reactants (in this case, diamond). This is because adding heat to an exothermic reaction will drive the reaction backward to absorb the excess heat. Therefore, higher temperatures are not favorable for the formation of diamond.

### Step 5: Consider Pressure Effects
Next, we look at the densities of diamond and graphite. The density of diamond is 3.5 g/mL, while the density of graphite is 2.3 g/mL. Since diamond has a higher density, increasing the pressure will favor the formation of the phase with lower density, which is graphite. However, we need to consider that the reaction is in equilibrium, and we want to favor the formation of diamond.

### Step 6: Combine the Effects
To favor the formation of diamond, we need to apply high pressure and low temperature. High pressure will push the equilibrium toward the side with fewer moles (if applicable) or the side with a lower density. However, since we are looking for conditions that favor diamond formation, we conclude that high pressure is favorable.

### Conclusion
The favorable conditions for the formation of diamond from graphite are:
- **High Pressure**
- **Low Temperature**

Thus, the correct answer would be high pressure and low temperature.

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