The boiling points of HF, HCl, HBr and HI follow the order

• HF> HCl > HBr > HI

• HF> HI> HBr > HCl

• HI> HBr > HCl> H

• HCl > HF> HBr > HI

The energy required to break one mole of hydrogen-hydrogen bonds in H₂ is 436 kJ. What is the longest wavelength of light required to break a single hydrogen-hydrogen bond?

• 68.5nm

• 137nm

• 274nm

• 584nm

The correct order of O-O bond lenght in O_2, H₂O_2, and O₃

• O₂> O₃> H₂O₂

• H₂O₂ > O₃ > O₂

• O₃> O₂> H₂O₂

• O₃ > H₂O₂> O₂

The number of $\mathrm{\sigma }$ and $\mathrm{\pi }$ bonds between two carbon atoms in calcium carbide are

• $\mathrm{one} \mathrm{\sigma }, \mathrm{one} \mathrm{\pi }$

• $\mathrm{one} \mathrm{\sigma }, \mathrm{two} \mathrm{\pi }$

• $\mathrm{two} \mathrm{\sigma }, \mathrm{one} \mathrm{\pi }$

• $\mathrm{one} \mathrm{\sigma }, 1\frac{1}{2}\mathrm{\pi }$

An element E loses one $\mathrm{\alpha }$ and two $\mathrm{\beta }$ particles in three successive stages. The resulting elemenl wiil be

• an isobar of E

• an isotone of E

• an isotope of E

• E itself

An element X belongs to fourth period and fifteenth group of the periodic table. Which of the following statements is true?

• It has completely filled s-orbital and a partially filled d-orbital.

• It has completely filled s-and p -orbitals and a partially filled d-orbital.

• It has completely filled s- and p-orbitals and a half filled d-orbital.

• It has a half filled p -orbital and completely filled s-and d-orbitals.

Which of the following plots represent an exothermic reaction?

The condition for a reaction to occur spontaneously is

• $∆$H must be negative

• $∆$S must be negative

• $\left(∆\mathrm{H}-\mathrm{T}∆\mathrm{S}\right)$ must be negative

• $\left(∆\mathrm{H}+\mathrm{T}∆\mathrm{S}\right)$ must be negative

The molar solubility (in mol L^-1) of a sparingly soluble salt MX₄ is 'S'. The corresponding solubility product is K_sp in terms of 'K_sp' is given by the relation

• $\mathrm{S}={\left(\frac{{\mathrm{K}}_{\mathrm{sp}}}{128}\right)}^{1/4}$

• $\mathrm{S}={\left(\frac{{\mathrm{K}}_{\mathrm{sp}}}{256}\right)}^{1/5}$

• S=(256 K_sp)^1/5

• S=(128 K_sp)^1/4

The time taken for an electron to complete one revolution in Bohr orbit of hydrogen atom is

• $\frac{4{\mathrm{m}}^2{\mathrm{\pi r}}^2}{{\mathrm{n}}^2{\mathrm{h}}^2}$

• $\frac{{\mathrm{n}}^2{\mathrm{h}}^2}{4{\mathrm{mr}}^2}$

• $\frac{4{\mathrm{\pi }}^2{\mathrm{mr}}^2}{\mathrm{nh}}$

• $\frac{\mathrm{nh}}{4{\mathrm{\pi }}^2{\mathrm{mr}}^2}$