A balloon containing 1 mole air at 1 atm initially is filled further with air till pressure increases to 4 atm. The initial diameter of the balloon is 1 m and the pressure at each stage is proportion to diameter of the ballon. How many no. of moles of air added to change the pressure from 1 atm to 4 atm
255
P∝d P = kd and k=1 atm1 metre
PV=nRT kd(16πd3) = nRT;
d41d42=n1n2; 144=n1/n2; n2=256
no. of moles added = 256 - 1 = 255