A negative catalyst will :

Options

A. raise the energy of activation for a given reaction
B. take away the energy of reactants and deactivate them
C. catalyse the backward reaction more than the forward one, thereby shifting equilibrium backward.
D. None of these

Explanation

To solve the question regarding the effect of a negative catalyst, we will analyze each of the provided options step by step.

### Step 1: Understand the concept of a negative catalyst
A negative catalyst, also known as an inhibitor, is a substance that decreases the rate of a chemical reaction. It does this by increasing the activation energy required for the reaction to occur.

**Hint:** Recall that catalysts generally lower the activation energy, while negative catalysts do the opposite.

### Step 2: Evaluate the first option
**Option A:** "Raise the energy of activation for a given reaction."
- This statement is true. A negative catalyst increases the activation energy, which results in a decrease in the reaction rate.

**Hint:** Think about how activation energy affects the speed of a reaction.

### Step 3: Evaluate the second option
**Option B:** "Take away the energy of reactants and deactivate them."
- This statement is incorrect. A negative catalyst does not take away energy from the reactants; instead, it raises the activation energy barrier.

**Hint:** Consider what it means to "deactivate" reactants and whether that aligns with the role of a negative catalyst.

### Step 4: Evaluate the third option
**Option C:** "Catalyze the backward reaction more than the forward one thereby shifting equilibrium backward."
- This statement is also incorrect. A negative catalyst does not shift the equilibrium position; it affects the rate of the reaction but does not favor either the forward or backward direction.

**Hint:** Remember that catalysts (positive or negative) do not change the position of equilibrium.

### Step 5: Evaluate the fourth option
**Option D:** "None of these."
- Since we have already established that Option A is correct, this option is incorrect.

**Hint:** Check if any of the previous options are valid before concluding that none are correct.

### Conclusion
Based on the analysis of the options:
- The correct answer is **Option A:** "Raise the energy of activation for a given reaction."

**Final Answer:** A negative catalyst will raise the energy of activation for a given reaction.