After losing a number of $\alpha$ and $\beta$ particles,$_{92}U^{238}$ is changed to $_{82}Pb^{206}$. The total number of $\alpha$-particles lost in this process is:

One junction of a certain thermoelectric couple is at a fixed temperature $T_r$ and the other junction is at temperature $T$. The thermo-electromotive force for this is expressed by $E=k(T-T_r)[T_0-\frac{1}{2}(T+T_r)]$. At temperature $T=\frac{1}{2} T_0$,the thermoelectric power is

$_6 C^{12}$ and $_1 T^3$ are formed in nature due to the nuclear reaction of a neutron with:

The relation between pressure $p$ and volume $V$ is given by $p V^{1/4} = \text{constant}$. If the percentage decrease in volume is $\frac{1}{2} \%$,then the percentage increase in pressure is:

Which of the following statements is correct?

$A$ metal $M$ and its compound can give the following observable changes in a sequence of reactions: $M$ $\xrightarrow{\text{dil. } HNO_3} M(NO_3)_2$ $\xrightarrow{NaOH} \text{White ppt.}$ $\xrightarrow{\text{Excess } NaOH} \text{Colourless solution}$ $\xrightarrow{H_2S} \text{White ppt.}$. Identify the metal $M$.