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A bar of pure gold is heated to 95.0 degrees Celsius. The specific heat capacity of gold is 1.29 X 10^2. The gold is placed into 500 mL of ethyl alcohol initially at a temperature of 25 Celsius. The final temperature of the mixture is 27.0 Celsius. What is the mass of the gold?

Sagot :

First we have to use conservation of energy, that the heat transferred from gold to the alcohol used to raise the temperature of the alcohol by 2 degrees. 
     the heat lost by gold = heat required by the methyl 
   (m of gold)(C of gold)(dTof gold) = (m of ethyl)(C of ethyl)(dT of ethyl) 
m of gold is the unknown to be determined
c of gold is the specific heat of gold
dT of gold is the change in temperature in gold
m of ethyl is the mass of ethyl alcohol
C of ethyl is the specific heat of ethyl
dT is the change in temperature in ethyl alcohol
                                        mass of gold = unknown
                                               c of gold = 129
                                  dT of gold = 95 - 25 = 68 degrees
                     m of ethyl = density of ethyl * volume of ethyl
                              789 X 0.5 X 10^(-3) = 0.3945
                                 mass of gold = 0.3945 kg