Which of the following chemical reaction(s) is/are involved in developing of photographic plate?

Options

A. `C_(6)H_(4)(OH)_(2)+2AgBr to 2Ag+C_(6)H_(4)O_(2)+2HBr`
B. `AgBr+2Na_(2)S_(2)O_(3) to Na_(3)[Ag(S_(2)O_(3))_(2)]+NaBr`
C. `2AgNO_(3)+Na_(2)S_(2)O_(3) to Ag_(2)S_(2)O_(3)+2NaNO_(3)`
D. `AgNO_(3)+KCN to AgCN+KNO_(3)`

Explanation

To determine which chemical reactions are involved in the development of a photographic plate, we can analyze the two main steps that take place during this process.

### Step 1: Reaction Involving Phenol and Silver Bromide
The first step in developing a photographic plate involves the reaction of phenol (C6H4OH) with silver bromide (AgBr). The reaction can be represented as follows:

1. **Chemical Reaction**:
\[ 2 \, \text{C}_6\text{H}_4\text{OH} + 2 \, \text{AgBr} \rightarrow 2 \, \text{Ag} + \text{C}_6\text{H}_4\text{O}_2 + 2 \, \text{HBr} \]

In this reaction, phenol reacts with silver bromide to produce metallic silver (Ag), which forms the image on the photographic plate, along with the byproducts of benzoquinone (C6H4O2) and hydrobromic acid (HBr).

### Step 2: Washing Out Unreacted Silver Bromide
The second step involves removing any unreacted silver bromide from the photographic plate. This is done using sodium thiosulfate (Na2S2O3), which acts as a fixing agent. The reaction can be represented as follows:

2. **Chemical Reaction**:
\[ 2 \, \text{Na}_2\text{S}_2\text{O}_3 + 2 \, \text{AgBr} \rightarrow 2 \, \text{NaBr} + \text{Na}_3\text{AgS}_2\text{O}_3 \]

In this reaction, sodium thiosulfate reacts with the unreacted silver bromide to form a soluble complex (Na3AgS2O3) and sodium bromide (NaBr), effectively washing away the unreacted AgBr.

### Conclusion
Both of these reactions are essential for the development of a photographic plate. The first reaction creates the image by reducing silver ions to metallic silver, while the second reaction removes any excess silver bromide that did not react.

### Final Answer
Thus, the correct options for the reactions involved in developing a photographic plate are both the first and second reactions.

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