Please help with these questions! 1) A spherical balloon is made from a material
ID: 2242492 • Letter: P
Question
Please help with these questions!
1) A spherical balloon is made from a material whose mass is 3.00 kg. The thickness of the material is negligible compared to the 1.4 m radius of the balloon. The balloon is filled with helium (He) at a temperature of 304 K and just floats in air, neither rising nor falling. The density of the surrounding air is 1.19 kg/m3. Find the absolute pressure of the helium gas.
2) Calculate the number of gas molecules in a container of volume 0.20 m3 filled with gas under a partial vacuum of pressure 10 Pa at 19
Explanation / Answer
1)
V_ballon =(4/3)pir^3 =(4/3)*pi*1.4^3
V_ballon =11.5 m^3
W_ballon =F_B =W_airdisplaced
(m_ballon+m_he)*g=p_air*V_ballon*g
=>m_he =p_air*V_ballon-m_ballon =1.19*11.5-3
m_he =10.68 Kg
n =m_he/mass per mole =10.68/4.0026*10^-3=2667.74
PV=nRT
P =nRT/V =2667.74*8.314*304/11.5
P=5.86*10^5 pa or 586.3 Kpa
2)
T=273+19 =292 K
PV=nKT
10*0.2 =n*1.38*10^-23*292
n =4.96*10^20 3)
3)
T=19+272=292 K
Q=nRTln(V2/V1)
given
V2=4V1
Q=7*8.314*292*ln(4)
Q=23558.43 J