Question

ethylene glycol is a colorless liquid at room temperature with the following properties:

melting point is -12.9°C.

boiling point 197.3°C

heat of fusion is 159.50 J/g

heat of vaporization is 1056.87 J/g

heat capacity of the liquid is 2.41 J/g°C

heat capacity of the gas 1.25 J/g°C

If you had a sample of ethylene glycol at -10°C, what state would it be in (solid, liquid, or gas) if you decreased the temperature from -10°C to -20°C what phase change would it go through? (melting, freezing, boiling, condensation, sublimation, no change) If you had 5.00g of solid ethylene glycol at -12.9°C, how much energy would be used to take the sample to 10°C? (use 4 sig figs and no unit)

Answer 1

Melting point of ethylene glycol is -12.9°C. Therefore, it will be in liquid state at -10°C.

If the temperature is decreased to -20°C it will freeze.

Using the formula

ΔT = q/ m x Cs (heat capacity of liquid)

m = 5 g

ΔT = Initial Temperature – Final Temperature

       = -12.9 – 10

       = -22.9 °C

Rearranging equation to give q i.e. heat

q = ΔT x m/Cs

    = -22.9 x 5/2.41

    = -47.510

As the heat/energy was taken from the system, value is in negative.