For doping silicon with boron, silicon specimen was kept in gaseous atmosphere containing B2O3 that maintained the B concentration at the surface of Si specimen at the level of 3*10^26 boron atoms/m^3. The process was carried out at 1100 degrees C. The diffusion coefficient of B in Si at 1100 degrees C is 4*10^-13 cm^2/s. Calculate the concentration of B at the depth of 10^-4 cm from the surface after 130 minutes of diffusion at 1100 degrees C

Chromosome 17 is made of over million base pairs.

)benzene and toluene form nearly ideal solutions. consider an equimolar solution of benzene and toluene. at 20 °c the vapour pressures of pure benzene and toluene are 9.9 kpa and 2.9 kpa, respectively. the solution is boiled by reducing the external pressure below the vapour pressure. calculate (i) the pressure when boiling begins, (ii) the composition of each component in the vapour, and (iii) the vapour pressure when only a few drops of liquid remain. assume that the rate of vaporization is low enough for the temperature to remain constant at 20 °c.

Describe the forces both attractive and repulsive that occur as two atoms move closer together.