At higher altitude,the boiling point of water is $95\,^{\circ}C$. The amount of $NaCl$ added to $1\, kg$ of water $(K_b = 0.52\, K\, kg\, mol^{-1})$ in order to raise the boiling point of the solution to $100\,^{\circ}C$ (assuming $90\%$ ionization of $NaCl$) is ........... $g$.

$A$ neutral atom has $2, 8,$ and $7$ electrons in $K, L,$ and $M$ shells respectively. What is the total number of electrons in the $p$-orbitals?

Which of the following substances would quickly absorb oxygen?

The pattern of standing waves formed on a stretched string at two instants of time (extreme and mean positions) is shown in the figure. The velocity of the two waves superimposing to form stationary waves is $360 \ m/s$ and their frequency is $256 \ Hz$. Which of the following is not a possible value of $t$ (in $sec$)?

The period of $\sin ^4 x + \cos ^4 x$ is

If the pair of straight lines $xy-x-y+1=0$ and the line $ax+2y-3a=0$ are concurrent,then $a$ is equal to