Question

What will be the concentration of an atrazine solution if 2 kg of Atrataf (50% a.i. of atrazine) is mixed in 100 litres of water?

• A. 0.2 %
• B. 2.0 %
• C. 0.1 %
• D. 1.0 %

Hint:

Find the actual weight of atrazine in 2 kg of the 50% product, then divide by the weight of the water used.

Answer 1

The Correct Option is D

Step 1: Write down the given data.
Weight of Atrataf formulation used = 2 kg = 2000 g.
Active ingredient (a.i.) content of the formulation = 50%, so pure atrazine makes up half of this weight.
Volume of water used to prepare the spray solution = 100 litres.

Step 2: Find the weight of pure atrazine (the active ingredient).
\[ \text{Weight of a.i.} = 2000 \times \frac{50}{100} = 1000 \text{ g} \]
So 2 kg of the 50% formulation contains 1000 g, or 1 kg, of pure atrazine.

Step 3: Convert the water volume to a matching weight unit.
Percentage concentration of a spray solution is worked out as weight of active ingredient divided by the total weight of the solution, taking 1 litre of water as about 1000 g, since water's density is close to 1 g per mL.
\[ 100 \text{ litres} = 100 \times 1000 = 100000 \text{ g} \]

Step 4: Calculate the percentage concentration.
\[ \% \text{ concentration} = \frac{\text{weight of a.i.}}{\text{weight of solution}} \times 100 \]
\[ = \frac{1000}{100000} \times 100 = 1.0\% \]

Step 5: Final Answer.
The atrazine spray solution works out to 1.0% concentration. Checking the arithmetic directly: 2000 g at 50% a.i. gives 1000 g of pure atrazine, and 1000 g spread through 100000 g (100 litres) of water gives exactly 1%, which matches option 4 among the given choices. If a different water volume had been intended, the answer would scale up or down, but 100 litres is the value consistent with one of the four options given here. \[ \boxed{1.0\%} \]