A 2.50-g sample of powdered zinc is added to 100.0 mL of a 2.00-M aqueous solution of hydrobromic acid in a calorimeter with a total heat capacity of 448 J/K. The observed increase in temperature is 21.1 K at a constant pressure of one bar. Using these data, calculate the standard enthalpy of reaction. Zn(s) + 2HBr(aq) --- ZnBr2(aq) + H2(g)

Question

A 2.50-g sample of powdered zinc is added to 100.0 mL of a 2.00-M aqueous solution of hydrobromic acid in a calorimeter with a total heat capacity of 448 J/K. The observed increase in temperature is 21.1 K at a constant pressure of one bar. Using these data, calculate the standard enthalpy of reaction. Zn(s) + 2HBr(aq) ---> ZnBr2(aq) + H2(g)

DrBob222 · Answer

heat emitted (absorbed by the calorimeter) = q
I am under the impression that 448 J/K is the Ccal WITHOUT the added water. You will need to adjust the answer if that isn't the case and 448 J/K is the total heat capacity of the SYSTEM.
Q = [mass H2O x specific heat H2O x 21.1] + [Ccal x 21.1] = ?
Then q/gram is q/2.5g Zn and q/mol = q/g x 65.39. You can change to kJ/mol which is the way they usually are reported.

John · Answer

How do you convert that to kJ/mol