List of practice Questions

A 12pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor?

Explain what would happen if in the capacitor given in Exercise 2.8, a 3 mm thick mica sheet (of dielectric constant = 6) were inserted between the plates,

(a) while the voltage supply remained connected.

(b) after the supply was disconnected.

(a)and(b)show the refraction of a ray in air incident at 60° with the normal to a glass-air and water-air interface, respectively. Predict the angle of refraction in glass when the angle of incidence in water is 45° with the normal to a water-glass interface

Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel.

(a) What is the total capacitance of the combination?

(b) Determine the charge on each capacitor if the combination is connected to a 100 V supply.

A point charge \(+10 µC\) is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)

Although phenoxide ion has more number of resonating structures than carboxylate ion,carboxylic acid is a stronger acid than phenol.Why?

Two charges 2 μC and –2 μC are placed at points A and B 6 cm apart.

(a) Identify an equipotential surface of the system.

(b) What is the direction of the electric field at every point on this surface?

A 4.5cm needle is placed 12cm away from a convex mirror of focal length 15cm. Give the location of the image and the magnification.Describe what happens as the needle is moved farther from the mirror.

Calculate the half-life of a first order reaction from their rate constants given below:

\(200\ s^{-1 }\)
\(2 \ min^{-1 }\)
\(4\ years^{-1}\)

A regular hexagon of side 10 cm has a charge 5 μC at each of its vertices. Calculate the potential at the centre of the hexagon.

The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.

Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is \(8.0 × 10^3 N m^2 C^{-1}. \)
(a) What is the net charge inside the box?
(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or Why not?

A small candle,2.5cm in size is placed at 27cm in front of a concave mirror of radius of curvature 36cm.At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image.If the is moved closer to the mirror, how would the screen have to be moved?

Calculate the amount of benzoic acid \((C_6H_5COOH)\) required for preparing 250 mL of 0.15 M solution in methanol.

Nalorphene \( (C_{19}H_{21}NO_3 )\), similar to morphine, is used to combat withdrawal symptoms in narcotic users. Dose of nalorphene generally given is 1.5 mg. Calculate the mass of \(1.5 \times 10^{–3} m\) aqueous solution required for the above dose.

Consider a uniform electric field \(E = 3 × 10^3 \,\hat{i} NC^{-1}\).
(a) What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the yz - plane?
(b) What is the flux through the same square if the normal to its plane makes a \( 60^0\) angle with the x-axis?

Calculate the mass percentage of aspirin \((C_9H_8O_4 )\) in acetonitrile \((CH_3CN)\) when 6.5 g of \(C_9H_8O_4\) is dissolved in 450 g of \(CH_3CN.\)

When 3-methyl butane-2-ol is treated with HBr, the following reaction takes place:
Give a mechanism for this reaction. (Hint: The secondary carbocation formed in step II rearranges to a more stable tertiary carbocation by a hydride ion shift from 3rd carbon atom

Show how would you synthesise the following alcohols from appropriate alkenes?

If the solubility product of CuS is \(6 × 10^{–16}\), calculate the maximum molarity of CuS in aqueous solution.

A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is \(1.5 × 10^3 NC^{-1}\) and points radially inward, what is the net charge on the sphere?

An organic compound contains 69.77% carbon,11.63% hydrogen and rest oxygen.The molecular mass of the compound is 86.It does not reduce Tollens’ reagent but forms an addition compound with sodium hydrogensulphite and give positive iodoform test.On vigorous oxidation it gives ethanoic andpropanoic acid.Writethe possible structure of the compound.

Write the mechanism of the reaction of HI with methoxymethane.

If the density of some lake water is \(1.25g mL^{–1}\) and contains 92 g of \(Na^+\) ions per kg of water, calculate the molality of \(Na^+\) ions in the lake

Explain the fact that in aryl alkyl ethers

(i)the alkoxy group activates the benzene ring towards electrophilic substitution and

(ii)it directs the incoming substituents to ortho and para positions in the benzene ring.