Acylinder contains 250 g of helium at 200 k. the external pressure is constant at 1 atm. the temperature of the system is raised by 74 k. calculate the heat lost or gained by the system. calculate your answer to three significant figures and express you answer in j. heat capacity for helium = 20.8 j/(mol k) molecular weight for helium = 4 g/mol

There is 96200 J or 96 kJ of heat released.

Explanation:

Step 1: Data given

Mass of helium = 250 grams

Temperature = 200 K

Temperature is raised by 74 K

The heat capacity of helium = 20.8 J/mol*K

Molecular weight for helium = 4 g/mol

Step 2: Calculate moles of Helium

Moles of Helium = mass of Helium / molar mass of helium

Moles of helium = 250 grams / 4g/mol

Moles of helium = 62.5 moles

Step 3: Calculate heat

Q = n*c*ΔT  or

⇒ with Q = the heat released in Joule

⇒ with n = moles of helium = 62.5 moles

⇒ with c = the heat capacity of helium = 20.8 J/mol*K

⇒ with ΔT = the change in temperature = T2 - T1 = 74 K

Q = 62.5 mol * 20.8 J/mol*K * 74 K

Q = 96200 J = 96 kJ

Since the temperature is raised, this is an exothermic reaction. The heat is released.

There is 96200 J or 96 kJ of heat released.

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c is the answer because when something is left after something evaporates that shows the chemical change.