A balloon vendor at a street fair is using a tank of helium to fill her balloons. The tank has a volume of 124.0 L and a pressure of 104.0 atm at 24.0 °C. After a while she notices that the valve has not been closed properly. The pressure had dropped to 94.0 atm. (The tank is still at 24.0 °C.)How many moles of gas has she lost?

She lost 50.88 moles

Explanation:

Step 1: Data given

The volume of the tank = 124.0 L

The initial pressure = 104.0 atm

The temperature = 24.0 °C = 297 K

The pressure drops to 94.0 atm

The temperature stays constant at 297 K

Step 2: Calculate the initial number of moles

p*V = n*R*T

n = (p*V)/(R*T)

⇒with p = the initial pressure = 104.0 atm

⇒with V = the initial volume = 124.0 L

⇒with n = the initial number of moles = TO BE DETERMINED

⇒with R = the gas constant = 0.08206 L*atm/mol*K

⇒ with T = the temperature= 297 K

n = (104.0*124.0)/(0.08206*297)

n = 529.14 moles

Step 3: Calculate final number of moles

p*V = n*R*T

n = (p*V)/(R*T)

⇒with p = the initial pressure = 94.0 atm

⇒with V = the initial volume = 124.0 L

⇒with n = the initial number of moles = TO BE DETERMINED

⇒with R = the gas constant = 0.08206 L*atm/mol*K

⇒ with T = the temperature= 297 K

n = (94.0*124.0)/(0.08206*297)

n = 478.26 moles

Step 4: Calculate the difference of moles

529.14 moles - 478.26 moles = 50.88 moles

She lost 50.88 moles

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.