CHEMISTRY QUESTION (multiple choice answers) ?

2020-04-13 8:54 pm

A balloon containing helium is tied to the pole of a stand-in an amusement park and has a volume of 12 L at a temperature of 20°C. After some time it is observed that its volume has decreased and is 11.5 L. Knowing for sure that the balloon did not lose gas, what happened?
-the pressure will have remained the same but the temperature has increased by about 10°C.-the temperature will have remained the same but the pressure has decreased by 0.5 atm-the temperature will have remained the same but the pressure has increased by 0.5 atm-the pressure will have remained the same but the temperature has dropped by about 10°C.

回答 (1)

micatkie

2020-04-13 9:46 pm

✔ 最佳答案

There are two possible ways to decrease the volume of a gas: increase the pressure or decrease the temperature. Hence, we should only consider the third and the fourth options.

Consider the third option:
Original: P₁ = 1.0 atm, V₁ = 12 L
At constant temperature: P₁V₁ = P₂V₂ .. ⇒ .. V₂ = V₁ × (P₁/P₂)
New volume, V₂ = (12 L) × (1.0/1.5) = 8 L ≠ 11.5 L
Hence, rule out the third option.

Consider the fourth option:
Original: V₁ = 12 L, T₁ = (273 + 20) K = 293 K
New: V₂ = ? L, T₂ = (273 + 10) K = 283 K
At constant pressure: V₁/T₁ = V₂/T₂ .. ⇒ .. V₂ = V₁ × (T₂/T₁)
New volume, V₂ = (12 L) × (283/293) = 11.6 L ≈ 11.5 L

The answer: the pressure will have remained the same but the temperature has dropped by about 10°C.

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