4hcl + o2 ⇌ 2h2o + cl2

which of the following would result from increasing the volume of oxygen?
the volume of hydrochloric acid increases.
the rate of forward reaction increases.
the rate of backward reaction increases.
the volume of water vapor decreases.

The rate of forward reaction increases.

Explanation:

Increasing the volume of oxygen:

will increase the concentration of oxygen (reactants), so the equilibrium will be shifted to the right side (products side) to suppress the effect of increasing the volume of oxygen.

So, the right choice is: The rate of forward reaction increases.

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.