Question

0.009 g of CaCO\(_3\) is dissolved in 1 litre of solution. Calculate the concentration of the solution in parts per million (ppm).

• A. 0.009 ppm
• B. 0.9 ppm
• C. 9 ppm
• D. 90 ppm

Hint:

To quickly calculate ppm for any aqueous solution, just remember that 1 ppm = 1 mg/L. Simply convert your solute mass to milligrams and divide by the volume in litres!

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Parts per million (ppm) is a unit of concentration that expresses the mass of solute per one million parts of total mass of the solution. For dilute aqueous solutions, the density of the solution is approximately equal to that of pure water ($1\ \text{g/mL}$ or $1\ \text{kg/L}$).
Step 2: Key Formula or Approach:
The formula for ppm is: \[ \text{ppm} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 10^6 \] Alternatively, for dilute aqueous solutions, $1\ \text{ppm} = 1\ \text{mg/L}$.
Step 3: Detailed Explanation:
Given:
Mass of solute ($\text{CaCO}_3$) = $0.009\ \text{g}$
Volume of solution = $1\ \text{litre}$
First, convert the mass of the solute from grams to milligrams: \[ 0.009\ \text{g} = 0.009 \times 1000\ \text{mg} = 9\ \text{mg} \] Since the volume is $1\ \text{L}$, the concentration in mg/L is: \[ \text{Concentration} = \frac{9\ \text{mg}}{1\ \text{L}} = 9\ \text{mg/L} \] Because $1\ \text{mg/L}$ is equivalent to $1\ \text{ppm}$ in dilute aqueous solutions, the concentration is $9\ \text{ppm}$.
Step 4: Final Answer:
The concentration of the solution is $9\ \text{ppm}$.