The number of moles of gas that was in the water bottle is 0.015 moles
where p = gas pressure
v = volume of gas
n = number of moles of gas
R = molar gas constant
T = temperature
making n subject of the formula
from the data provided, assuming the gas filled up the water bottle:
n = 0.75 * 0.5 / 0.082 * 295
n = 0.015 moles
Therefore, the number of moles of gas that was in the water bottle is 0.015 moles
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