The molar enthalpies of combustion of $C_2H_{2(g)}$,$C_{(graphite)}$,and $H_{2(g)}$ are $-1300$,$-394$,and $-286 \ kJ \ mol^{-1}$,respectively. The standard enthalpy of formation of $C_2H_{2(g)}$ is ....... $kJ \ mol^{-1}$.

$A$ point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at a distance of $9 \ m$ and $25 \ m$ respectively from the source. The ratio of the amplitudes of the waves at $P$ and $Q$ is

Let $f(x)=e^x$,$g(x)=\sin ^{-1} x$ and $h(x)=f(g(x))$,then $\frac{h^{\prime}(x)}{h(x)}$ is equal to

What is meant by floral formula ? Which signs are used to make floral formula ?

Which of the following animals is not viviparous?

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: