. A cylindrical balloon of 21 cm diameter is to be filled up
with H2 at NTP from a cylinder containing the gas at 20 atm at 27°C The cylinder can hold 2.82 litre of water at NTP. Calculate the number of balloons that can be filled up.
Answer: Volume of 1 balloon which has to be filled = 4/3 π (21/2)3 = 4851 ml = 4.851 litre
Let n balloons be filled, then volume of H2 occupied by balloons = 4.851 × n
Also, cylinder will not be empty and it will occupy volume of H2 = 2.82 litre.
Total volume occupied by H2 at NTP = 4.851 × n + 2.82 litre
P2 = 1 atm Available H2
V1 = 4.851 × n + 2.82 P2 = 20 atm
T1 = 273K T2 = 300K
V2 = 2.82 litre
P1V1 /T1= P2V2/T2
or 1 × (4.85n + 2.82)/273 = 20 × 2.82/300
n = 10