The electrons which take part in order to exhibit variable oxidation states by transition metals are

Photoelectric emission is observed from a metallic surface for frequencies $v_1$ and $v_2$ of the incident light rays $(v_1 > v_2)$. If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of $1 : k$,then the threshold frequency of the metallic surface is

When acetaldehyde is reacted with $LiAlH_4$,what is the product formed?

The thermo emf of a thermocouple is given by $E = aT + bT^2$,where $\frac{a}{b} = -200^{\circ}C$. If the cold junction is kept at $30^{\circ}C$,then the inversion temperature is ($\varepsilon$ in volt,$T$ in centigrade). (in $K$)

Which of the following halogens has the highest bond dissociation energy?

The value of $\lambda$ with $|\lambda| < 16$ such that $2 x^2 - 10 x y + 12 y^2 + 5 x + \lambda y - 3 = 0$ represents a pair of straight lines,is