Question

How many grams of water at 25 C must be mixed in an insulated container with 250 grams of water at 93 C if the final temperature of the combined water is to be 75 C.

Answer 1

Answer:

Explanation

Comment

Normally you would just use m*c*delta T. But the c is the same in both cases, so you need just use m*deltaT

Givens

25 degrees

m = ?

T = 25

t = final temp = 75

93 degrees

m = 250

T = 93

t = final temp = 75

Solution

(t - 25)*m = (93 - t) * 250                   Remove the brackets

75*m - 25m = 93*250 -  250*75      Combine the right

m(75 - 25) = 23250 - 250*75

50 m = 23250 - 18750                      Combine

50 m = 4500                                      Divide both sides by 50

50*m/50 = 4500/50

m = 90

Answer: 90 grams are needed.