Which of the following processes is a non-spontaneous process?

Options

A. Dissolution of salt of sugar in water
B. Mixing of different gases through diffusion
C. Precipitation of copper when zinc rod is dipped in aqueous solution of copper sulphate
D. Flow of heat from a cold body to a hot body in contact

Answer

To determine which of the given processes is a non-spontaneous process, we need to analyze each option based on the definitions of spontaneous and non-spontaneous processes.

### Step-by-Step Solution:

1. **Understand Spontaneous and Non-Spontaneous Processes**:
- A **spontaneous process** is one that occurs naturally without any external influence. It is characterized by a negative change in Gibbs free energy (ΔG < 0).
- A **non-spontaneous process** requires external energy or influence to occur and has a positive change in Gibbs free energy (ΔG > 0).

2. **Evaluate Each Option**:
- **Option 1: Dissolution of salt or sugar in water**:
- This process occurs naturally as sugar or salt dissolves in water without any external help. Therefore, it is a **spontaneous process**.

- **Option 2: Mixing of different gases through diffusion**:
- The diffusion of gases happens naturally as they mix without any external influence. Thus, this is also a **spontaneous process**.

- **Option 3: Precipitation of copper when a zinc rod is dipped in copper sulfate solution**:
- This is a chemical reaction that occurs naturally due to the reactivity of zinc with copper ions. Therefore, this is a **spontaneous process**.

- **Option 4: Flow of heat from a cold body to a hot body in contact**:
- This process does not occur naturally; heat flows from a hot body to a cold body. For heat to flow from a cold body to a hot body, external work must be done (like in a refrigerator). Hence, this is a **non-spontaneous process**.

3. **Conclusion**:
- Based on the analysis, the process that is non-spontaneous is **Option 4: Flow of heat from a cold body to a hot body in contact**.

### Final Answer:
The non-spontaneous process is **Option 4: Flow of heat from a cold body to a hot body in contact**.