4Na + O2 —> 2Na2O
In this chemical reaction, how many moles of Na2O will be produced if 2.90 moles of Na react completely? Express answer to three significant figures.

3.91g

Explanation:

1. Use the equation mol = mass/Mr (Molecular Formula)

2. Use the information you have and put it into the formula 2.9/23 = 0.1260869565

3. Multiply 0.1260869565 by 62 (molecular formula of Na2O) - Formula rearranged to mass = mol × Molecular formula = 7.817391303

4. Divide by two to get two moles, as shown in the chemical equation

5. 3.9086956515

6. 3.91g to three significant figures

the answer is option a.

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.