Class 12th

What is the apparent molecular mass (in gm/mol) of a weak acid, HA (molar mass = 30.0 gm/mol) in an aqueous solution, which shows elevation in boiling point by $0.0156°C?$  

[Given: pK_a (HA) = 2.0, K_b (H₂O) = 0.52 K kg mol^-1]

Hydrogenation of the above compound in the presence of poisoned palladium catalyst gives

Initially the capacitor is uncharged. What is the steady state charge on it $\left(in\mu C\right)$  after the switch is closed?

In gravity free space, a bead of charge $1\mu C$ and mass 3mg is threaded on a rough rod of friction coefficient $\mu$ = 0.3. A magnetic field of magnitude 0.2 T exists perpendicular to the rod. The bead is projected along the rod with a speed 4m/s. How much distance (in m) will the bead cover before coming to rest?

You are given a converging lens with equal radii of curvature and a diverging lens with the same radii of curvature as those of the converging lens. The lenses are made of material with n = 1.50, the radii of curvature are all 35cm. They are placed at opposite ends of a tube 15cm long, and the nearer lens which is converging is 10cm from an object. What is the location of the image that results from the two refractions? Write the final distance (in cm) from diverging lens.

In the circuit in figure we have ${\epsilon }_1={\epsilon }_2$  = 100V, R₁ = 20 $\Omega$ , R₂ = 10 $\Omega$ , R₃ = 40 $\Omega$  and R₄ = 30 $\Omega$ . Find the reading of the ammeter (in A). Disregard the resistance of the battery and the ammeter.

An electron moves in the field produced by a charged sphere of radius 10cm along the radius connecting the points separated by 12 and 15 cm from the centre of the sphere. The velocity of the electron changes thereby from 2 * 10⁵ to 2 * 10⁶ m/s. Determine the surface charge (in nC/m²) density of the sphere. (Mass of electron = 9.1 * 10^-31kg)

You are trying to construct a compound microscope given two lenses with focal lengths f₁ = 1.0cm and f₂ = 4.0cm. How far apart (in cm) should you place the lenses in order to obtain an angular magnification of 60? (Assume normal adjustment of microscope)

When light of wavelength 540 nm passes through a single slit of unknown width, the diffraction pattern displays a second maximum where the first minimum of light of an unknown wavelength had been observed to fall. What is the unknown wavelength?