`B(OH)_(3)+NaOH to Na[B(OH)_(4)](aq).`
Then addition of which of the following shifts the reaction in the backward direction.

Options

A. Glycerol
B. Mannitol
C. Catechol
D. Ethanol

Explanation

To determine which addition shifts the reaction \( B(OH)_3 + NaOH \rightarrow Na[B(OH)_4](aq) \) in the backward direction, we will apply Le Chatelier's principle. Here’s a step-by-step solution:

### Step 1: Understand the Reaction
The reaction involves orthoboric acid (\( B(OH)_3 \)) reacting with sodium hydroxide (\( NaOH \)) to form sodium metaborate (\( Na[B(OH)_4] \)).

### Step 2: Apply Le Chatelier's Principle
Le Chatelier's principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In this case, if we want to shift the equilibrium to the left (backward direction), we need to increase the concentration of the reactants or remove the products.

### Step 3: Identify Possible Additives
We need to consider which substances can be added to increase the concentration of the reactants or decrease the concentration of the products. The options provided are:
1. Glycerol
2. Mannitol
3. Catechol
4. Ethanol

### Step 4: Analyze Each Option
- **Glycerol**: A triol that may not effectively shift the equilibrium backward due to its bulky structure.
- **Mannitol**: A sugar alcohol with multiple hydroxyl groups, which may also not effectively shift the equilibrium backward.
- **Catechol**: An aromatic compound with hydroxyl groups, which is bulky and may not favor the backward reaction.
- **Ethanol**: A simple alcohol that can effectively react with water and help in the removal of water from the system, thereby shifting the equilibrium backward.

### Step 5: Conclusion
Among the options, adding **Ethanol** would effectively shift the reaction in the backward direction by removing water through a condensation reaction, thus increasing the concentration of the reactants.

### Final Answer
The addition of **Ethanol** shifts the reaction in the backward direction.

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