Thus, the first chlorinated organic insecticide is DDT, making (D) the correct answer.
DDT (dichlorodiphenyltrichloroethane) is one of the first chlorinated organic insecticides prepared. It was synthesized by Paul Hermann Müller in 1939 and became widely used for controlling insect-borne diseases like malaria.
Match the following:
List-I (Metal in drinking water) | List-II (Maximum prescribed concentration in ppm) |
---|---|
A) Mn | I) \( 0.05 \) |
B) Zn | II) \( 3.0 \) |
C) Cd | III) \( 0.005 \) |
D) Cu | IV) \( 5.0 \) |
A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force \( F = 20 \, \text{N} \) acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take \( g = 10 \, \text{m/s}^2 \)):