Addition of a solute to pure water causes

Options

A. negative water potential
B. more negative water potential
C. positive water potential
D. more positive water potential

Answer

### Step-by-Step Solution:

1. **Understanding Water Potential**: Water potential (Ψw) is a measure of the potential energy in water and is influenced by solute concentration and pressure. It is represented in units of pressure (usually megapascals, MPa). Pure water has a water potential of zero (Ψw = 0).

2. **Effect of Adding Solute**: When a solute is added to pure water, it affects the concentration of water molecules. The presence of solute particles reduces the number of free water molecules, which in turn decreases the water potential.

3. **Defining Water Potential with Solute**: The addition of solute results in a more negative water potential. This is because the solute potential (Ψs) becomes negative. The overall water potential can be expressed as:
\[ Ψw = Ψs + Ψp \]
where Ψp is the pressure potential. In this case, since we are only considering the solute, we can focus on Ψs.

4. **Conclusion**: Since pure water has a water potential of zero, adding a solute will decrease the water potential, making it negative. Therefore, the correct answer to the question is that the addition of a solute to pure water causes a **negative water potential**.

### Final Answer:
The addition of a solute to pure water causes **negative water potential**.

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