Which of the following statements are true? I. The number of protons in an element is always the same for all neutral atoms of that element. II. The number of electrons in an element is always the same for all neutral atoms and ions of that element. III. The number of neutrons in any element is always equal to the number of protons of that element. IV. The number of neutrons in an element can sometimes vary – resulting in the formation of an unstable isotope that is slightly more (or less) massive than the stable atom of the same element. Group of answer choices I, II, and IV are true I, II, and III are true II and III are true I and II are true I and IV are true

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"

the answer is c

tell me if wrong

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.