Final answer:
By applying Boyle's Law, which states that the pressure and volume of a gas are inversely related at constant temperature, the initial pressure of the dry oxygen was calculated to be 980 mmHg before expansion.
Step-by-step explanation:
The problem you're trying to solve relates to the behavior of gases under different conditions of pressure and volume, while keeping the temperature constant. This scenario is a demonstration of Boyle's Law, which states that for a given mass and constant temperature of a gas, the pressure inversely varies with the volume. The formula given by Boyle's Law is P1 x V1 = P2 x V2, where P1 and V1 are the initial pressure and volume, respectively, and P2 and V2 are the final pressure and volume.
According to the information provided:
- Initial Volume (V1) = 5 dm³
- Final Volume (V2) = 7 dm³
- Final Pressure (P2) = 700 mmHg
To find the initial pressure (P1), we rearrange the formula to:
P1 = (P2 x V2) / V1
P1 = (700 mmHg x 7 dm³) / 5 dm³
P1 = 980 mmHg
Therefore, the initial pressure of the gas was 980 mmHg assuming that the temperature remains constant.