4p + 5O2 -> P4O10 ; the percent yield of PO4O10 when 6.20 g of phosphorus burns into excess oxygen is 67.0%. What is the yield of P4O10?

   36.9 g

Explanation:

P4 + 5O2 = P4O10  Balanced equation

moles P4 present = 23.9 g x 1 mole/123.88 g = 0.193 moles

moles O2 present = 20.8 g x 1 mol/32 g = 0.65 moles O2

From balanced equation, mole ratio O2 : P4 is 5:1.  Is 0.65 moles O2 5x 0.193 moles?  NO.  You don't have enough O2.

O2 is limiting in this reaction.

theoretical moles of P4O10 = 0.65 moles O2 x 1 mole P4O10/5 moles O2 = 0.13 moles P4O10

mass of P4O10 produced = 0.13 moles x 283.9 g = 36.9 g

a boiling water reactor does not boil the water. a pressurized water reactor boils the water faster. a pressurized water reactor is heated directly by the core. a pressurized water reactor does not use fission.

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.