In the concentration of $PbS$ containing $ZnS$ as impurity,the depressant used is:

$A$ beam of light $AO$ is incident on a glass slab $(\mu = 1.54)$ in a direction as shown in the figure. The reflected ray $OB$ is passed through a Nicol prism. On viewing through the Nicol prism,we find on rotating the prism that:

Which of the following is not a characteristic property of chemical equilibrium?

$BX_3 + NH_3 \xrightarrow{R.T} BX_3 \cdot NH_3 + \text{Heat of adduct formation } (\Delta H)$. The numerical value of $\Delta H$ is found to be maximum for:

The events $A$ and $B$ have probabilities $0.25$ and $0.50$,respectively. The probability that both $A$ and $B$ occur simultaneously is $0.14$. Then,the probability that neither $A$ nor $B$ occurs is:

In the Victor-Meyer's test,the colours given by $1^o$,$2^o$ and $3^o$ alcohols are respectively: