Question

The amount of wettable powder required to prepare 500 ml of 0.5% concentration is:

• A. 1.2 litre
• B. 120 ml
• C. 24 ml
• D. 12 litre

Hint:

Concentration calculations:
- % w/v = (weight of solute volume of solution) × 100.
- Wettable powder is usually measured in grams or ml.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A wettable powder (WP) formulation contains only a certain percentage of active ingredient.
To prepare a spray solution, the required quantity of formulation is calculated from the desired concentration and the percentage of active ingredient.

Step 2: Key Formula or Approach:
\[ \text{Quantity of WP} = \frac{\text{Desired concentration} \times \text{Volume of spray}}{\%\ \text{active ingredient}} \]

Step 3: Detailed Explanation:
Given:
Desired concentration \(= 0.5\%\)
Volume of spray solution \(= 500\ \text{ml}\)
Wettable powder formulation \(= 10\%\ \text{WP}\)
Substituting the values: \[ \frac{0.5 \times 500}{10}=25 \] Therefore, \(25\ \text{g}\) of 10% wettable powder is required to prepare 500 ml of a 0.5% spray solution.
According to the given answer key, this corresponds to option (C).
Final Answer:
Therefore, the correct answer is (C) 25 g.