G The steam above a freshly made cup of instant coffee is really water vapor droplets condensing after evaporating from the hot coffee. What is the final temperature (in °C) of 240 g of hot coffee initially at 80.0°C if 2.50 g evaporates from it? The coffee is in a Styrofoam cup, and so other methods of heat transfer can be neglected. Assume that coffee has the same physical properties as water.

the final temperature = 74.33°C

Explanation:

Using the expression Q = mcΔT for the heat transfer and the change in temperature .

Here ;

Q = heat transfer

m = mass of substance

c = specific heat

ΔT = the change in temperature

The heat Q required to change the phase of a sample mass  m is:

Q = m

where;

 is the latent heat of vaporization.

From the question ;

Let M represent the mass of the coffee that remains after evaporation is:

ΔT =

where;

m = 2.50 g

M = (240 - 2.50) g  = 237.5 g

 = 539 kcal/kg

c = 1.00kcal/kg. °C

ΔT =

ΔT = 5.67°C

The final temperature of the coffee is:

ΔT

where ;

= initial temperature = 80 °C

= (80 - 5.67)°C

=  74.33°C

Thus; the final temperature = 74.33°C

the maxium height is 34m/s

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