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101 Chem 101
Question 16 of 18
Which of the following phase changes is endothermic?

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Explanation:

It's an ideal gas problem:

first, we will use this formula to get V2:

P1V1/T1 = P2V2/T2

when the Pressure still constant:

∴ V1/T1 = V2/ T2

when V1 = 2 L

T1 = 25 °C

T2 = 49°C

∴2 L /25°C = V2 / 49

∴V2 = 3.92 L

then we will use this formula to get no. of moles:

P2V2 = nRT

when P2 =P1 = 3.5 atm

V2 = 3.92

R= 0.0821

T2 = 49°C +273 = 322 K

by substitution:

∴3.5 atm * 3.92 L = n * 0.0821 * 322 K

∴n = 0.5 mol

∴ no.of moles = 0.5 mol