Which of the following compounds lacks iron?

An ideal gas expands in such a way that $PV^2 = \text{constant}$ throughout the process.

An elevator weighing $6000\, kg$ is pulled upward by a cable with an acceleration of $5\, m/s^2$. Taking $g$ to be $10\, m/s^2$,then the tension in the cable is ........... $N$.

Which one of the following reactions does not form a gaseous product?

$A$ stone of mass $m$ is tied to a string and is moved in a vertical circle of radius $r$ making $n$ revolutions per minute. The total tension in the string when the stone is at its lowest point is

When $100\,V$ $DC$ is applied across a solenoid,a current of $1\,A$ flows in it. When $100\,V$ $AC$ is applied across the same coil,the current drops to $0.5\,A$. If the frequency of the $AC$ source is $50\,Hz$,the impedance and inductance of the solenoid are: