Question

My mass 100 kg. But I want to fly in the sky with the help of balloons. Each balloon contain 20 moles of H₂(g) at the atmospheric temperature 300 K and at pressure of 0.05 atm. The mass of each balloon is 2.5 kg. The density of air = 1.25 gm/L and g = 10 m/s² . How many minimum such balloon do I need to attach with myself to fly in the sky ?

• A. 11
• B. 12
• C. 13
• D. 14

Answer 1

Answer: (A)

11

Answer 2

Press. of gas = 760 + 80 = 840 mm of Hg.

vol. of each balloon =$\frac{20 \times 0.082 \times 300}{0.05}$= 9840 L

Let n no. of balloon required.

\ upward force = n × 9840 × 1.25 × 10^–3 × g.

Downward force = 100 × g + n × 20 × 2 ×10^–3 × g + n × 2.5 × g

\ g × n × 9840 × 1.25 × 10^–3 = 100g + 40n × 10^–3 × g + 2.5 ng

or 12.3 n – 2.5 n – 0.04 n, = 100

or 9.76 n = 100

or n = 10.24

\ Minimum 11 balloons are required.