| List-I (Species) | List-II (Maximum allowed concentration in ppm in drinking water) | ||
| A | F- | I | < 50 ppm |
| B | \(SO^{2-}_4\) | II | < 5 ppm |
| C | \(NO^-_3\) | III | < 2 ppm |
| D | Zn | IV | < 500 ppm |
Choose the correct answer from the options given below :
A. F$^-$ (Fluoride): The allowed concentration is less than 1.5 ppm, but for safe drinking water, it is set at $<$ 50 ppm.
B. SO$_4^{2-}$ (Sulfates): Allowed concentration is up to $<$ 500 ppm to prevent taste or odor changes in water.
C. NO$_3$ (Nitrates): The maximum safe limit is $<$ 2 ppm to avoid health effects like methemoglobinemia.
D. Zn (Zinc): Safe concentration is $<$ 500 ppm to maintain taste quality and health safety.
Thus, the correct matching is A-I, B-II, C-III, D-IV.
Solute A associates in water. When 0.7 g of solute A is dissolved in 42.0 gof water, it depresses the freezing point by 0.2°C. The percentage association of solute A in water is :
[Given : Molar mass of A = 93 g mol–1. Molal depression constant of water is 1.86 K kg mol–1.]
Inductance of a coil with \(10^4\) turns is \(10\,\text{mH}\) and it is connected to a DC source of \(10\,\text{V}\) with internal resistance \(10\,\Omega\). The energy density in the inductor when the current reaches \( \left(\frac{1}{e}\right) \) of its maximum value is \[ \alpha \pi \times \frac{1}{e^2}\ \text{J m}^{-3}. \] The value of \( \alpha \) is _________.
\[ (\mu_0 = 4\pi \times 10^{-7}\ \text{TmA}^{-1}) \]
A small block of mass \(m\) slides down from the top of a frictionless inclined surface, while the inclined plane is moving towards left with constant acceleration \(a_0\). The angle between the inclined plane and ground is \(\theta\) and its base length is \(L\). Assuming that initially the small block is at the top of the inclined plane, the time it takes to reach the lowest point of the inclined plane is _______. 