5 litre of a solution contains 25 mg of `CaCO_(3)`. What is its concentration in ppm? (mol.wt of `CaCO_(3)` is 100)

Options

A. 25
B. 1
C. 5
D. 250

Explanation

To find the concentration of CaCO₃ in parts per million (ppm), we can follow these steps:

### Step 1: Understand the Definition of ppm
Parts per million (ppm) is defined as the mass of solute (in grams) present in 1 million grams of solution.

### Step 2: Convert the Volume of Solution to Mass
We are given that the volume of the solution is 5 liters. To convert this to mass, we can use the density of water, which is approximately 1 g/mL.

\[ \text{Mass of solution} = \text{Density} \times \text{Volume} \]
\[ \text{Mass of solution} = 1 \, \text{g/mL} \times 5000 \, \text{mL} = 5000 \, \text{g} \]

### Step 3: Convert the Mass of CaCO₃ to Grams
The mass of CaCO₃ given is 25 mg. We need to convert this to grams:

\[ 25 \, \text{mg} = 25 \times 10^{-3} \, \text{g} = 0.025 \, \text{g} \]

### Step 4: Calculate the Concentration in ppm
Now we can use the formula for ppm:

\[ \text{ppm} = \left( \frac{\text{mass of solute (g)}}{\text{mass of solution (g)}} \right) \times 10^6 \]
Substituting the values we have:

\[ \text{ppm} = \left( \frac{0.025 \, \text{g}}{5000 \, \text{g}} \right) \times 10^6 \]

### Step 5: Simplify the Expression
Calculating the fraction:

\[ \frac{0.025}{5000} = 5 \times 10^{-6} \]

Now, multiplying by \(10^6\):

\[ \text{ppm} = 5 \times 10^{-6} \times 10^6 = 5 \]

### Conclusion
The concentration of CaCO₃ in the solution is **5 ppm**.

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