Which of the following concentration of metals in drinking water is
not prescribed-

Options

A. Fe 0.2 ppm
B. Cu 3.0 ppm
C. Cd 2.0 ppm
D. Zn 5.0 ppm

Answer

To determine which concentration of metals in drinking water is not prescribed, we need to analyze the acceptable limits for each metal based on international standards. Here’s a step-by-step solution:

### Step 1: Identify the Metals and Their Prescribed Concentrations
We need to look at the metals mentioned in the question and their respective limits:
- **Iron (Fe³⁺)**: 0.2 ppm
- **Copper (Cu²⁺)**: 3.0 ppm
- **Cadmium (Cd²⁺)**: 0.005 ppm
- **Zinc (Zn²⁺)**: 5.0 ppm

### Step 2: Analyze Each Metal's Concentration
Now, we will analyze whether each metal's concentration is within the prescribed limits:
- **Iron**: 0.2 ppm is acceptable.
- **Copper**: 3.0 ppm is acceptable.
- **Cadmium**: 0.005 ppm is acceptable but very low due to its toxicity.
- **Zinc**: 5.0 ppm is acceptable.

### Step 3: Identify the Metal with the Lowest Acceptable Limit
From the analysis, we see that cadmium has the lowest acceptable limit (0.005 ppm), which indicates that it is highly regulated due to its toxicity.

### Step 4: Conclusion
Since cadmium has a very low limit and is highly toxic, it is the metal concentration that is not typically prescribed in drinking water due to its potential harm even at low levels. Therefore, the answer to the question is **Cadmium (Cd²⁺)**.

### Final Answer
**Cadmium (Cd²⁺) is the concentration of metal in drinking water that is not prescribed.**

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