The answer is 2.78 moles of Si
C. 14
you would subtract the mass number from the protons or the atomic number because in order to find the mass number you would add the protons and neutrons :)
The statement that is incorrect I believe would be A. The amount of matter increases slightly as water changes state.
Answer : The new pressure if the volume changes to 560.0 mL is, 280 mmHg
Explanation :
According to the Boyle's, law, the pressure of the gas is inversely proportional to the volume of gas at constant temperature and moles of gas.

or,

where,
= initial pressure = 560.00 mmHg
= final pressure = ?
= initial volume = 280 mL
= final volume = 560.0 mL
Now put all the given values in the above formula, we get:


Therefore, the new pressure if the volume changes to 560.0 mL is, 280 mmHg