A restaurant waiter pours 400 ml of steaming hot coffee (essentially water, at 8

Question

A restaurant waiter pours 400 ml of steaming hot coffee (essentially water, at 85 Degree C) filling a ceramic mug (at room temperature - please estimate it for this problem). The mass of the mug is equal to the mass of the coffee it holds. What is the final temperature of this mug of coffee? Do you think it would scald you, or is it cool enough to drink? Now, add two 25 gram ice cubes to the cup. After it has melted, temperature of the coffee? Do you think it s too hot to drink, too cool, or about right?

Explanation / Answer

a) qlost = qgain
q = cmdT
Coffee----mug
cmdT = cmdT
4 * m * (85-x) = 0.752 * m * (x-20)

85 - x = 0.188*( x - 20)

85 - x = 0.188x - 3.76

1.188*x = 88.76

x = 74.71 C

b) Temperature is too high to drink. it will scald you.

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