Neon is generally used in sign boards. If is emits strongly at 616 nm, calculate:
number of quanto present if it produces 2 energy.

Calculate the number of molecules present in 0.5 moles of CO2 ?

Calculate the total number of electrons present in 2.3g of ethane.

Infrared lamps are used in restaurants to keep the food warm. The infrared radiation is strongly absorbed by water, raising its temperature and that of the food. If the wavelength of infrared radiationis assumed to be 1500 nm, and the number of quanta of infrared radiation produced per second by an infrared lamp (that consumes enregy at the rate of 100 W and is 12% effcient only) is (xx10^(19) , then the value of x is : (Given: h= 6.665xx10^(-34)J-s)

An element (density 7.2 gcm^-3) crystallizes in a body centred cubic structure having its unit cell edge length 2.88oversetcircA . Calculate the number of atoms present in 156 g of the element.

A certain particle carries 2. 5 xx 10 ^(-16) C of static electric charge. Calculate the number of electrons present in it.

In a photoelectric effect set up, a point source of light of power 3.2 xx10^(-3) W emits monoenergetic photons of energy 5eV.The source is located at a distance of a stationary metallic sphere of work function 3eV and radius 8xx10^(-3)m .The efficiency of photoelectron emission is one for every 10^(6) incident photons.Assume that the sphere is isolated and initially neutral and the photoelectrons are initially swept away after emission. Calculate the number of photoelectrons emitted per second.

Long Answer Questions Five mark Each QUESTIONS FROM CBSE BOARD EXAMINATIONS : A flower of tomato plant following the process of sexual reproduction produces 240 viable seeds. Answer the following questions giving reasons: (a) What is the minimum number of pollen grains that must have been involved in the pollination of its pistil? (b) What would have been the minimum number of ovules present in the ovary? (c) How many megaspore mother cells were involved? (d) What is the minimum number of microspore mother cells involved in the above case? (e) How many male gametes were involved in this case?

9 moles of "D" and 14 moles of E are allowed to react in a closed vessel according to given reactions. Calculate number of moles of B formed in the end of reaction, if 4 moles of G are present in reaction vessel. (percentage yield of reaction is mentioned in the reaction) Step -1 3D+4E 80%rarr5C+A Step-2 3C+5G 50%rarr 6B+F

During the discharge of a lead storage battery, the density of sulphuric acid fell down from 1.294 to 1.139 g/ml. Sulphuric acid of density 1.294g/ml is 39% H_2SO_4 by weight and that of density of 1.139 g/ml is 20% H_2SO_4 by weight. The battery holds 3.5 L of acid and the volume remains practically constant during discharge. calculate the number of ampere hours for which the battery must have been used. The charging and discharging reactions are: Pb^(2+)+SO_4^(2-)LeftrightarrowPbSO_4+2bare(Charging) PbO_2+4H^(+)+SO_4^(2-)+2bareLeftrightarrowPbSO_4+2H2O(Discharging) .

A certain day absorbs lights of lamda=400 nm and then fluorescence light of wavelength 500 nm. Assuming that under given condition 40% of the absorbed energy is re-emitted as fluorescence, calculate the ratio of quanta absorbed to number of quanta emitted out.