"The properties of elements are periodic functions of their atomic weights." This periodic law was given by

Catechol and \(\mathrm{m}\)-cresol respectively are

Identify the correct statements from the following
I. \(\mathrm{B}_2 \mathrm{H}_6\) is an electron deficient hydride.
II. \(\mathrm{NH}_3\) an electron rich hydride.
III. \(\mathrm{NaH}\) is a covalent hydride.
IV. \(\mathrm{YbH}_{255}\) is an interstitial hydride.

A metal crystallizes in two phases, one as $\mathrm{fcc}$ and another as $\mathrm{bcc}$ with unit cell edge lengths of $3.5\stackrel{°}{ \mathrm{A}}$ and $3.0\stackrel{°}{ \mathrm{A}}$, respectively. The ratio of density of $\mathrm{fcc}$ and $\mathrm{bcc}$ phases approximately is

Given below are two statements
Assertion (A): Protium and deuterium differ in their rates of reactions.
Reason (R): They have different enthalpies of bond dissociation.
The correct answer is

When ' \(\mathrm{X}\) ' \(\mathrm{g}\) of graphite is completely burnt in a bomb calorimeter in excess of \(\mathrm{O}_2\) at \(298 \mathrm{~K}\) and \(1 \mathrm{~atm}\) pressure as given in the equation
\(\mathrm{C}\) (graphite) \(+\mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2(\mathrm{~g})\)
The temperature of calorimeter raised from \(298 \mathrm{~K}\) to \(302 \mathrm{~K}\). If the heat capacity of the calorimeter and molar enthalpy change for the reaction at \(1 \mathrm{~atm}\) and \(298 \mathrm{~K}\) are \(20.7 \mathrm{~kJ} \mathrm{~K}^{-1}\) and \(-248.4 \mathrm{~kJ} \mathrm{~mol}^{-1}\), ' \(\mathrm{X}^{\prime}\) in \(\mathrm{g}\) is

Which one of the following halogen compounds is least reactive towards hydrolysis by \(\mathrm{S}_{\mathrm{N}} 1\) mechanism ?

The device used for voltage regulation is

Along the \(x\)-axis, three charges \(\frac{q}{2},-q\) and \(\frac{q}{2}\) are placed at \(x=0, x=a\) and \(x=2 a\) respectively. The resultant electric potential at a point \(P\) located at a distance \(r\) from the charge \(-q(a < r)\) is \(\left(\varepsilon_0\right.\) is the permittivity of free space)

The points on the curve \(y=\frac{2}{3} x^3+\frac{1}{2} x^2\), where the tangents make equal angles with coordinate axes are

If \(50 \%\) of \(1 \mathrm{M} \mathrm{Na}_2 \mathrm{SO}_4\) is dissociated in aqueous solution of density \(1.2 \mathrm{~g} \mathrm{~mL}^{-1}\), what is the molality of \(\mathrm{Na}^{+}\)ion in the solution?

The locus of a point which moves such that the area of the triangle formed by it with the vertices \((1,2)\) and \((-2,5)\) is 8 sq. units is/are

Water from a tap emerges vertically downwards with initial velocity \(4 \mathrm{~ms}^{-1}\). The cross-sectional area of the tap is \(A\). The flow is steady and pressure is constant throughout the stream of water. The distance \(h\) vertically below the tap, where the cross-sectional area of the stream becomes \(\left(\frac{2}{3}\right) A\), is \(\left(g=10 \mathrm{~m} / \mathrm{s}^2\right)\)