Which of the following oxides of nitrogen is a blue solid?

$A$ Carnot engine,having an efficiency of $\eta = 1/10$ as a heat engine,is used as a refrigerator. If the work done on the system is $10 \ J$,the amount of energy absorbed from the reservoir at a lower temperature is .......... $J$.

$A$ black body radiates energy at the rate of $E \text{ W/m}^2$ at a high temperature $T \text{ K}$. When the temperature is reduced to $\left(\frac{T}{2}\right) \text{ K}$,the radiant energy is

If $X$ is a Poisson variate such that $P(X=1)=P(X=2)$, then $P(X=4)$ is equal to

If the terminal speed of a sphere of gold (density $= 19.5 \,kg/m^3$) is $0.2 \,m/s$ in a viscous liquid (density $= 1.5 \,kg/m^3$),find the terminal speed of a sphere of silver (density $= 10.5 \,kg/m^3$) of the same size in the same liquid.

The chemical reaction that involves the roasting process is