Final answer:
The initial temperature (Ti) of the gas is 291.15 K.
Step-by-step explanation:
To solve this problem, we can use the relationship between volume and temperature at constant pressure, known as Charles's Law. According to Charles's Law, the volume and temperature of a gas are directly proportional as long as the pressure and amount of gas are constant.
Using the formula V₁/T₁ = V₂/T₂, we can plug in the values given:
- Initial volume (V₁) = 2.80 L
- Initial temperature (T₁) = ?°C
- Final volume (V₂) = 1.75 L
- Final temperature (T₂) = 18.00 °C
Converting the temperatures to Kelvin (K), we have:
- T₁ = 2.80 L * (18.00 °C + 273.15 K) / 2.80 L = 18.00 °C + 273.15 K = 291.15 K
- T₂ = 1.75 L * (18.00 °C + 273.15 K) / 2.80 L = 18.00 °C + 273.15 K = 291.15 K
Therefore, the initial temperature (Ti) is 291.15 K.