If the change in the value of $g$ at a height $h$ above the surface of the earth is the same as at a depth $x$ below it,then (both $x$ and $h$ being much smaller than the radius of the earth)

Based on the following thermochemical equations:
$H_2O_{(g)} + C_{(s)} \to CO_{(g)} + H_{2(g)}; \Delta H = 131 \ kJ$
$CO_{(g)} + \frac{1}{2}O_{2(g)} \to CO_{2(g)}; \Delta H = -282 \ kJ$
$H_{2(g)} + \frac{1}{2}O_{2(g)} \to H_2O_{(g)}; \Delta H = -242 \ kJ$
$C_{(s)} + O_{2(g)} \to CO_{2(g)}; \Delta H = X \ kJ$
The value of $X$ will be $...... \ kJ$.

$A$ metal wire $PQ$ slides on parallel metallic rails having a separation of $0.25\ m$,each having negligible resistance. There is a $2\,\Omega$ resistor and a $10\ V$ battery as shown in the figure. $A$ uniform magnetic field of magnitude $0.5\ T$ is directed into the plane of the paper. $A$ force of $0.5\ N$ to the left is required to keep the wire $PQ$ moving with a constant speed to the right. With what speed is the wire $PQ$ moving? (Neglect self-inductance of the loop)

The incorrect statement regarding the following reactions is:
$XeF_6 + \text{Excess } H_2O \rightarrow 'X' + HF$
$XeF_6 + 2 H_2O \rightarrow 'Y' + HF$

$A$ spherical hollow is made in a lead sphere of radius $R$,such that its surface touches the outside surface of the lead sphere and passes through the center. What is the shift in the center of mass of the lead sphere due to the hollowing?

When $MgSO_4$ reacts with $NH_4OH$ and $Na_2HPO_4$,it forms a white crystalline substance. What is the formula of that substance?