When 42.1 grams of water at 80.9 degrees Celsius are added to an unknown amount of water at 20 degrees Celsius. The final temperature of the mixture is 54.8 degrees Celsius. Calculate the unknown mass of water originally at 20 degrees Celsius. For known mass: q = (42.1 g)*(54.8-80.9 C)*(4.184 J/g*C) = 4593.0258 J Now for unknown mass: m = q/C*deltaT 4593.0258 J/(4.184 J/g*C)*(54.8-20 C) = 31.5448 = 31.5 g??? Thanks.