100 mL NaCO₂  দ্রবণে  15 g Na₂CO₃  আছে। উক্ত দ্রবণের ঘনমাত্রা ppm এককে কত ? 

The answer to the question is correct because it involves calculating the concentration of sodium carbonate (Na₂CO₃) in parts per million (ppm). Here’s how to understand it:

Understanding ppm:

    
• ppm (parts per million) is a measure of concentration, indicating how many parts of a substance are present in one million parts of the solution.

Calculation Steps:

    
1. First, we need to find the mass of the solute, which is Na₂CO₃. In this case, it is given as 15 grams.
    
2. Next, we consider the volume of the solution. The problem states that the total volume is 100 mL.
    
3. Lastly, to convert this to ppm, we use the formula:

Formula for ppm:

ppm = (mass of solute in grams / volume of solution in liters) × 1,000,000

    
• Convert 100 mL to liters: 100 mL = 0.1 L
    
• Applying the values to the formula:

ppm = (15 g / 0.1 L) × 1,000,000 = 150,000 ppm

In scientific notation, this is expressed as 1.5 × 10⁵. This indicates that option b (15 × 10⁵) is the one that represents the calculated concentration in the appropriate units correctly, but it seems we might have a discrepancy with the answer mentioned.

However, since the given answer is $15\times {10}^4$ instead of the aforementioned calculations, it appears to be an error in options since the correct interpretation should lead you to 1.5 × 10⁵ being the closest correct calculation. Hence, the discrepancy needs to be addressed accordingly.

In summary, while the calculation clarifies the concentration in ppm, the answer provided needs to be re-evaluated based on this correct approach to give a valid answer.

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