The characteristics of chemical reaction is

Options

A. change in state
B. change in colour
C. both
D. none of these.

Answer

To answer the question about the characteristics of chemical reactions, we can break it down into several key points. Here’s a step-by-step solution:

### Step 1: Understand the Characteristics of Chemical Reactions
Chemical reactions have specific characteristics that can be observed. Some of these characteristics include:

1. **Change in State**: This refers to the transformation of reactants into products that may have different physical states (solid, liquid, gas).

2. **Change in Color**: A chemical reaction often results in a change in color, indicating that new substances have formed.

3. **Evolution of Gas**: Many chemical reactions produce gas as a product, which can be observed as bubbles or effervescence.

4. **Change in Temperature**: Some reactions either release heat (exothermic) or absorb heat (endothermic), leading to a change in temperature.

### Step 2: Example of Change in State
Consider the reaction between lead nitrate and potassium iodide. Both substances are in aqueous form (colorless). When they react, they form lead iodide, which is a solid yellow precipitate.

- **Chemical Equation**:
\[ \text{Pb(NO}_3\text{)}_2 (aq) + 2 \text{KI} (aq) \rightarrow \text{PbI}_2 (s) + 2 \text{KNO}_3 (aq) \]

This example illustrates a change in state from aqueous to solid.

### Step 3: Example of Change in Color
In the same reaction, the initial reactants (lead nitrate and potassium iodide) are colorless, but the product (lead iodide) is yellow. This change in color is another characteristic of a chemical reaction.

### Step 4: Conclusion
Based on the examples provided, we can conclude that both change in state and change in color are characteristics of chemical reactions. Therefore, both options A (Change in State) and B (Change in Color) are correct.

### Final Answer
Both A and B are characteristics of a chemical reaction.

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