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A sealed flask with a capacity of $$2 \text{ dm}^3$$ contains $$11 \text{ g}$$ of propane gas. The flask is so weak that it will burst if the pressure becomes $$2 \text{ MPa}$$. The minimum temperature at which the flask will burst is ______ °C. [Nearest integer]
(Given: $$R = 8.3 \text{ J K}^{-1} \text{ mol}^{-1}$$. Atomic masses of C and H are $$12u$$ and $$1u$$ respectively.) (Assume that propane behaves as an ideal gas.)
Correct Answer: 1655
We need to find the minimum temperature at which a sealed flask will burst.
Volume = $$2 \text{ dm}^3 = 2 \times 10^{-3} \text{ m}^3$$
Mass of propane = 11 g
Burst pressure = 2 MPa = $$2 \times 10^6 \text{ Pa}$$
$$R = 8.3 \text{ J K}^{-1} \text{ mol}^{-1}$$
Calculate moles of propane
Molecular formula of propane: $$C_3H_8$$
Molar mass = $$3 \times 12 + 8 \times 1 = 44 \text{ g/mol}$$
$$n = \frac{11}{44} = 0.25 \text{ mol}$$
Apply the ideal gas equation
$$PV = nRT$$
$$T = \frac{PV}{nR}$$
Substitute values
$$T = \frac{2 \times 10^6 \times 2 \times 10^{-3}}{0.25 \times 8.3}$$
$$T = \frac{4000}{2.075}$$
$$T = 1927.7 \text{ K}$$
Convert to Celsius
$$T = 1927.7 - 273 = 1654.7 \approx 1655 \text{ °C}$$
The answer is 1655.
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