Answer: Microscope
Explanation: This is a kid answering :)
The reaction between hydrogen and oxygen to form water is given as:

The balanced reaction is:

According to the balanced reaction,
4 g of hydrogen (
) reacts with 32 g of oxygen (
).
So, oxygen reacted with 29.4 g of hydrogen is:

Hence, the mass of oxygen that is reacted with 29.4 g of hydrogen is 235.2 g.
The more acidic the substance is, the more the iron nails will corrode (this obviously depends on what your experiment is but hope this helped in some way)