Class 12th

The sum of number of lone pairs of electrons present on the central atoms of XeO₃, XeOF₄ and XeF₆, is___________.

For the decomposition of azomethane,

CH₃N₂CH₃(g) → CH₃CH₃(g) + N₂(g), a first order reaction, the variation in partial pressure with time at 600 K is given as.

The half life of the reaction is __________* 10^-5s. [Nearest integer]

When the excited electron of a H atom from n = 5 drops to the ground state, the maximum number of emission lines observed are____________.

Magnetic flux (in weber) in a closed circuit of resistance $20\Omega$  varies with time t(s) as $?$  = 8t² – 9t + 5. The magnitude of the induced current at t = 0.25s will be _______mA.

A convex lens of focal length 20cm is placed in front of a convex mirror with principal axis coinciding each other. The distance between the lens and mirror is 10 cm. A point object is placed on principal axis at a distance of 60cm from the convex lens. The image formed by combination coincides the object itself. The focal length of the convex mirror is ______cm.

Two parallel plate capacitors of capacity C and 3C are connected in parallel combination and charged to a potential difference 18 F. The battery is then disconnected and the space between the plates of the capacitor of capacity C is completely filled with a material of dielectric constant 9. The final potential difference across the combination of capacitors will be ________V.

Two ideal diodes are connected in the network as shown is figure. The equivalent resistance between A and B is _______ $\Omega$ .

In a potentiometer arrangement, a cell of emf 1.20 V gives a balance point at 36cm length of wire. This cell is now replaced by another cell of emf 1.80 V. The difference in balancing length of potentiometer wire in above conditions will be ________cm.     

  $\frac{x}{x+4}$ is the ratio of energies of photons produced due to transition of an electron of hydrogen atom from its

(i) third permitted energy level to the second level and

(ii) the highest permitted energy level to the second permitted level.

The value of x will be ________.

The line of shortest distance between the lines $\frac{x-2}{0}=\frac{y-1}{1}=\frac{z}{1}$  and $\frac{x-3}{2}=\frac{y-5}{2}=\frac{z-5}{1}$  makes an angle of $co{s}^{-1}\left(\sqrt[]{\frac{2}{27}}\right)$  with the plane P : ax – y – z = 0, (a > 0). If the image of the point (1, 1, - 5) in the plane P is $(\alpha ,\beta ,\gamma ),$  then $\alpha +\beta -\gamma$  is equal to……….