The surface tension and vapour pressure of water at `20^@C` is `7.28 xx 10^-2 N m^-1` and `2.33 xx 10^3` Pa, respectively. What is the radius of the smallest spherical water droplet which can form without evaporating at `20^@C`?

The rate of constant of reaction at 300 K//320 K are 5 xx 10^(-4) s^(-1) and 2.0 xx 10^(-3)s^(-1) respectively. Calculate the value of activation energy of reaction.

A planet is revolving round the sun in elliptical orbit. The maximum and minimum distances of the planet from the sun are 2 xx 10^2 m and 2 xx 10^10 m respectively. The speed of the planet when it is nearest to sun is 2 xx 10^15 ms^-1 What is the speed when it is farthest to the sun?

The rate constants for the decomposition of HI at 283^@ C and 508^@ C are 3.517 xx 10^-7 and 3.954xx10^-2 respectively. Calculate the frequency factor at 283^@ C and energy of activation of the reaction.

What is the excess pressure inside a bubble of soap solution of radius 5.00 mm,given that the surface tension of soap solution at the temperature (20^@C) is 2.50xx 10 2 N in 1 ? If an air bubble of the same dimension were formed at depth of 40.0 cm inside a container containing the soap solution (of relative density 1.20), what would be the pressure inside the bubble ? (1 atmospheric pressure is 1.01xx 105 Pa).

Two point charges of +5xx10^-19C and +20 xx 10^-19 C are separated by a distance 2m. Find the point on the line joining them at which electric field intensity is zero.

The refractive index of glass is 1.5 and that of water is 1.3.If the speed of light in water is 2.25 xx 10^8 m s^(-1) ,what is the speed of light in glass?

The sap in trees, which consists aminly of water in summer, rises in a system of capilaries of radius r = 2.5 xx 10^-5 m. The surface tension of sap is T = 7.28 xx 10^-2 N m^-1 and the angle of contact is 0^@ . Does surface tension alone account for the supply of water to the top of all trees?

The procedure in was repeated for three further oil droplets. The magnitude of the charge on each of the droplets was found to be 3.2 xx 10^-19C, 6.4 xx 10^-19C and 3.2 xx 10^-19C . Explain what value these data and your answer in would guggest for the charge on the electron.