What is considered a species?

If an electric heater is rated at $1000\, W$,then the time required to heat one litre of water from $20\, ^oC$ to $60\, ^oC$ is

Let the function $g:(-\infty, \infty) \rightarrow \left(-\frac{\pi}{2}, \frac{\pi}{2}\right)$ be given by $g(u) = 2 \tan^{-1}(e^u) - \frac{\pi}{2}$. Then $g$ is

Two point white dots are $1\, mm$ apart on a black paper. They are viewed by an eye with a pupil diameter of $3\, mm$. Approximately,what is the maximum distance in $m$ at which these dots can be resolved by the eye? [Take wavelength of light $\lambda = 500\, nm$]

In which of the following species is the central atom $NOT$ surrounded by exactly $8$ valence electrons?

If $\overrightarrow{a}=\hat{i}+\hat{j}+\hat{k}$,$\overrightarrow{b}=\hat{i}+\hat{j}$,$\overrightarrow{c}=\hat{i}$ and $(\overrightarrow{a} \times \overrightarrow{b}) \times \overrightarrow{c}=\lambda \overrightarrow{a}+\mu \overrightarrow{b}$,then $\lambda+\mu$ is equal to: